The last of the verbs derived from a Latin sitting verb by
prefixation is sŭpersĕdēre or sŭpersĭdēre.  It was
formed from the prefix sŭper
‘over above’ and the verb sĕdēre ‘to
sit’.  There are versions of this verb attested with the root sĕd‑’s two allomorphs, ‑sĕd‑ and ‑sĭd‑. Its principal parts were sŭpersĕdĕo-sŭpersĭdĕo,
sŭpersĕdēre-sŭpersĭdēre,
supersēdī, supersessum.  This verb’s literal meaning was ‘to sit upon or above’,
and, derived from it, it could also mean, ‘to preside over’, ‘ to be superior
to’, and, more figuratively, ‘to abstain/refrain from doing something’.  This
verb has made it into English and Spanish, cf.  Eng.  supersede and Sp.  sobreseer. 
The two words are not good friends, however, since their meanings differe a great
deal.  In the Spanish word, we can still detect the original figurative meaning,
whereas the meaning of the English word had changed a great deal more. 

Eng.  supersede is
a mid-15th century loan, originally an intransitive verb with the meaning ‘to
postpone, defer (action), delay, hesitate’, from Middle French superceder or superseder, which had the same meaning, which is obviously derived
from the original Latin verb’s figurative meaning.  Middle French superseder was obviously a learned word,
a loanword from written Latin.  A common spelling error is to write this word as
supercede, with a c, in English, just like it was sometimes
also written in French.  Most English dictionaries condone this spelling as a legitimate
variant.  However, there is no doubt that the verb’s origin is in the Latin word
sĕdēre ‘to sit’ and not in the verb cēdĕre ‘to
proceed; to yield; etc.’,  source of Eng.  cede
and Sp.  ceder (cf.  Part II, Chapter 17). 
It is quite likely that the spelling ‘error’ is due to the semantic contrast of
the verb supersede (with an etymological
s) with the verb precede (with an etymological c),
which are sort of antonyms, since they can be paraphrased as ‘come after (and
replace)’ vs. ‘come before’ (cf.  Part I, Chapter 6,
§6.4.3). 

Modern French superséder is archaic, however, having been replaced with a patrimonial version of the word surseoir ‘to postpone, to defer something’, a word already attested at the end of the 11th century.  In the word surseoir, pronounced [syʀ.ˈswaʀ] in Modern French, we can see the Standard French patrimonial descendants of Lat.  sŭper, namely sur, and of sĕdēre, namely seoir.  It was originally an intransitive verb but by the beginning of the 13th century it was being used as a transitive verb, and by the 17th century it was what’s called an indirect transitive verb that requires a phrase with the preposition à ‘to’ to follow’.  Modern French surseoir is a formal, literary word and, mostly a legal term today, with the meaning ‘to postpone [a ruling (décision)]’, ‘to defer [a payment (versement)]’, or ‘to stay [the enforcement of a ruling (exécution)]’ (Oxford-Hachette Concise). 

The original meaning ‘postpone, defer’ of the Eng.  supersede is nowadays obsolete.  Over the years, this word took over new meanings, some of which are rare, if not archaic or obsolete.  It was used, for instance, as a legal term much like in French later on in the 15th century with the transitive meaning ‘to postpone or suspend the effecting of, defer, put off’, and by the 17th century, it meant ‘to put a stop to (legal proceedings, etc.);  to stop, stay’ (OED).  That, as we shall see, is the meaning that this word’s Spanish still has today. 

Also in the 17th century, the word was being used with the meaning ‘to make superfluous or unnecessary; to preclude the necessity of’ (OED) and, related to it, ‘to put another thing in the place of; to find or provide a replacement for’ (OED).  And that is pretty much the main meaning that the word has today, which is namely ‘to take the place of (something discarded or discontinued); to succeed to the place occupied by; to serve, be adopted, or be accepted instead of’ and ‘to take up the office of (someone removed or (formerly) promoted); to succeed and supplant in a position’ (OED).  Although today’s meaning of Eng.  supersede seems very different from the original one, we can easily see the evolution between the different meanings, which went from ‘postpone’, to ‘put a stop’, to ‘put a stop because it is unnecessary’, to ‘be unnecessary because there is something else in place’, to ‘ replace’ . 

The verb supersede is typically used in the passive voice, however, as to be superceded (by/with).  The way the OED describes it, the two senses of this passive verb are ‘to be discarded or discontinued as useless or obsolete; to be replaced by something else.  With by (a thing regarded as more advanced or superior)’ and ‘to be removed from or replaced in an office or position.  With by (the successor)’. 

The verb supersede translates into Spanish as reemplazar (cf.  Eng.  replace), substituir (cf.  Eng.  substitute), or suplantar (cf.  Eng.  supplant), or even desbancar ‘to supplant, replace, take the place of, to oust, displace, edge out’.  The passive participle superseded can be translated by any of the participles of any of the mentioned verbs, sustituido, remplazado/a, suplantado/a, desbancado/a, as well as by superado/a.

Sp.  sobreseer (conjugated like leer ‘to read’) is the descendant of this same Latin word, sŭpersĕdēre.  It has all the looks of a patrimonial word, since instead of the Latin prefix sŭper‑, we find its patrimonial Spanish descendant sobre‑, identical to the preposition sobre ‘over, above’.  Also, the other part of the word, sĕdēre, is missing the intervocalic ‑d‑, a common sound change in patrimonial words (cf.  Part I, Chapter 10).  It is not inconceivable, however, that this fancy word was a loan, most likely from French, one whose parts were somehow adapted to the patrimonial form of the descendants of the source words, sŭper and sĕdēre, in Spanish.  Unlike most patrimonial words, Sp.  sobreseer, which is already attested in the late 15th century, is not an everyday word but, rather, an uncommon legal term.  Its meaning is ‘to suspend an indictment investigation and, by extension, to put an end to legal proceedings’ (DLE).[a]

There aren’t many words that are related to either Eng.  supersede or Sp.  sobreseer.  Some dictionaries mention that the English noun that means ‘the act of superseding’ or ‘the state of being superseded’ is supersession, though the word is quite rare.  Even more rare is the adjective supersessive, found in some dictionaries and formed, in English, by means of the Latinate adjectival suffix ‑ive, which means ‘having the quality or character of supersession; taking the place of something or someone displaced’ (OED).  The word is formed according to the Latin pattern in which the adjective-forming suffix ‑īv‑ attaches itself to the passive participle stem of verbs, in this case supersess‑. The OED also mentions the rare noun supersessor, which has been used in English several times since 19th century and means ‘a person who or thing which supersedes another’ (OED).  This noun was also formed in English with the Latinate agent suffix ‑or, a descendant of Lat.  ‑ōr‑, which also attached itself to passive participle stems.  This word is a synonym of the word superseder, formed also in English, from the verb supersede by means of the English agent suffix ‑er. 

Finally, the name for the act of sobreseer in Spanish is sobreseimiento, a word derived, in Spanish, from the verb and the suffix ‑miento that creates nouns out of verbs.  It translates as dismissal or stay of proceedings.  There is no other word related to this verb in Spanish. 

At least one Latin verb, and perhaps two, was derived from a verb of sitting by means of the prefix sub‑ ‘under’.  It is not clear that there was a verb derived from Lat.  sĕdēre by means of this prefix, namely subsĭdēre (subsĭdĕo, subsĭdēre).  It does not appear in most Latin dictionaries, though some claim it existed and that it meant ‘to rest, stay, or remain in a place’.  What we know for sure, is that there was a verb derived by the prefix sub‑ from sĕdēre’s companion verb sīdĕre ‘to sit, settle’, namely subsīdĕre.[1] This verb meant ‘to sit down, crouch down, squat’, as well as ‘to sink down, settle down’.  The verb’s principal parts were (present indicative) subsīdō (present infinitive) subsīdĕre, (perfect active) subsēdī, (passive participle/supine) subsĕssus. 

This verb never made it into Spanish, either as a direct patrimonial descendant or as a loan.  English, however, did acquire it in the late 17th century in the form subside.  The original meaning of this word was ‘to sink down, fall to the bottom, precipitate’ (OED).  The word subside came into the language presumably directly from written Latin subsĭdēre, not through French which, like Spanish, does not have a reflex of this verb.  We should note, however, that there are two single, isolated attestations of an Old French verb soubseoir, now obsolete, meaning ‘to sink down’, from the late 14th and 15th centuries, a verb that is related to Old French seoir ‘to sit’, a patrimonial descendant of Lat.  sĕdēre.  Be that as it may, it does not seem to be the source of Eng.  subside, however.  Assuming that Latin is the source, however, the fact that the English verb subside is not taken from the passive participle subsĕssus of the Latin verb (which would have given us Eng. * subsess), but rather from a clipped form of the Latin infinitive subsĭdēre tells us that there is probably something else going on here, as we shall see. 

The English verb subside [səb.ˈsaɪ̯d] today has different meanings or senses in different contexts.  It is definitely a bit of a fancy word not used in colloquial speech.  When speaking of a building or a road, the verb subside means ‘to gradually sink to a lower level’ (DOCE), but this meaning is rather rare (less fancy synonyms: sink back, settle, cave in, fall in, collapse, give way, drop down,etc.).  Another rare or archaic meaning of this word is ‘to sink or settle down, as into a sofa’ (AHD) (less fancy synonyms: flop, sink, collapse; informal flump, plonk oneself, plop oneself).  Most of the time the verb’s subject refers to a departure from a normal situation and the verb has a meaning such as ‘to become less intense, violent, or severe until things gets back to normal’.  Said of water, and in particular flood water, subside means ‘it gradually goes underground or back to a normal level’ (DOCE), as in The floods finally subsided (less fancy synonyms: ebb, fall back, flow back, go down, get lower, abate, diminish).  It is also used to refer to extreme weather conditions getting back to normal, as in The wind gradually subsided (cf.  go down, get lower, abate, diminish).  Finally, when said of a feeling, pain, a sound or anything else that we detect through our senses, t means ‘to gradually become less strong until it ends or stops’, as in Finally the laughter subsided or The pain in my head has not subsided yet (cf.  let up, quiet down, ease (up), relent, die down, die out, peter out, taper off, lessen, remit, diminish, dwindle, weaken, fade, wane, ebb, slowly cease, come to a stop/end). 

The appropriate Spanish translation of the verb subside depends on what it is that subsides.  Speaking of land, a road or a building, hundirse may be used, a verb that literally means ‘to sink (down)’.  And the ‘sink into a sofa’ sense may translate as dejarse caer, lit. ‘ to let oneself (fall) down’.  The other, more common meanings of Eng.  subside may translate as amainar when speaking of a storm, rain, or wind; decrecer or bajar (de nivel) when speaking of flood waters; calmarse or disminuir when speaking of pain, anger, or excitement; remitir when speaking of a fever; and ir apagándose when speaking of things such as the sounds of applause or laughter. 

As we said, French did not have a verb derived from Lat.  subsīdĕre, but it did have a word subside, pronounced [syb.ˈzid] in Modern French, that comes indirectly from that verb, a cognate and the source of the English word subsidy.  Fr.  subside does not come directly from the Latin verb subsīdĕre, but rather from a noun derived from it, namely subsĭdĭum (sub‑sĭd‑ĭ‑um).[2] This word was originally referred to ‘the troops stationed in reserve in the third line of battle (behind the principes)’, that is to say ‘reserve, auxiliary, or support troops, reinforcements’.  From that meaning, it came to also mean, by extension, ‘support, assistance, aid, help, protection, etc.’ ( CTL).  The word subside is attested in French in the late 13th century, and even earlier in the century as succide, with the meaning ‘help, assistance, aid’.  By the 14th century, the word had acquired a meaning ‘contribution, tax’, and, later on, ‘pension, monetary help’ granted by the state or the government. 

Eng.  subsidy [ˈsʌb.sɪ.di] is a late 14th century loanword from Old French subside or, actually, from the Anglo-Norman dialect of Old French, which spelled it subsidie.  The main meaning of the English word subsidy today is ‘a sum of money granted from public funds’, which can be ‘to help an industry or business keep the price of a commodity or service low’, ‘to support an undertaking held to be in the public interest’ or, less commonly, for some other reason (COED). 

The Spanish word subsidio[sub.ˈsi.di̯o], cognate of Eng.  subsidy and Fr.  subside, has been around since the 15th century.  Although all three words involve transfer of money (monetary assistance), their meanings are not the same.  As we saw, the meaning of meanings of the English and French words are not the same and the meaning of Spanish subsidio is more like that of its French counterpart, where the word most likely came from.  The ‘tax’ meaning is secondary or archaic nowadays in Spanish, however, and the main meaning is ‘time-limited economic public assistance’, as in subsidio de paro/desempleo ‘unemployment compensation (US) or benefits (UK)’, and subsidio de enfermedad ‘sickness benefit’.  The main meaning of Eng.  subsidy, namely ‘money given to businesses’, translates into Spanish as subvención.[3]

From the nouns that we have just seen, both English and Spanish developed verbs that meant something like ‘to give monetary assistance’.  The two languages used different ways to derive the verb and so they cannot be said to have the same source or to be cognates.  The English verb is subsidize, formed by adding the Latinate suffix ‑ize to the word subsidy (minus the final letter): subsidy + ‑ize → subsidize (subsid‑ize).  The verb means ‘to support (an organization or activity) financially’ or ‘pay part of the cost of producing (something) to reduce its price’ (COED).  From the past participle of this verb comes the very common adjective subsidized by conversion which means ‘having partial financial support from public funds’ (WN), as in subsidized public housing. 

The Spanish verb derived from the noun subsidio is subsidiar, formed from the stem subsidi‑ of the noun subsidio (after removing the final inflectional ending ‑o), and the verbal infinitival inflectional ending ‑ar.  This word is used with the meaning ‘to give assistance to a person’, reflecting the main meaning of the noun subsidio, but it can also be used as a synonym of subvencionar, a verb derived from the noun subvención (see.  fn.  dd above), the main translation of Eng.  subsidy, and thus it can also mean ‘to give a subsidy (to a business or other entity)’. 

There are adjectives related to the nouns Eng.  subsidy ~ Sp.  subsidio, namely Eng.  subsidiary ~ Sp.  subsidiario/a, both of which mean ‘serving to assist or supplement; auxiliary’ (AHD) or ‘less important than but related or supplementary to something’ (COED).  Eng.  subsidiary also has a derived meaning when speaking of a company, namely ‘controlled by a holding or parent company’.  Actually, the adjective subsidiary can be used as a noun with the meaning ‘a company that is owned or controlled by another larger company’ (DOCE). 

Eng.  subsidiary and Sp.  subsidiario/a are loanwords from Lat.  subsĭdĭārĭus derived from Lat.  subsĭdĭum by means of the first-second conjugation adjective-forming suffix ‑āri‑(us/a/um) (sub‑sĭd‑ĭ‑ārĭ‑us).  In military language this word meant ‘of or belonging to a reserve, subsidiary’ and outside the military, ‘serving for support, subsidiary’ (L&S). 

Spanish subsidiario is not a very common adjective, less so than its English cognate, and it is rather formal.  It is used in formal expressions such as asignación subsidiaria ‘help allocation or allowance’.  Eng.  subsidiary much more commonly translates as secundario/a, complementario/a, or adicional (cf.  the English cognates of these words, secondary, complementary, and additional, which are synonyms of the different senses of the word subsidiary).  When referring to a firm that depends on a larger one, Eng.  subsidiary translates as filial, which can also be used as a noun, just like subsidiary can.  Sp.  filial is a loanword from Lat.  filĭālis, an adjective derived from the stem filĭ‑ of the noun filĭus ‘son’ or filĭa ‘daugher’, sourcewords of patrimonial Spanish hijo and hija (filĭ‑āl‑is). 

Finally, there is in English a rare noun subsidence [səb.ˈsaɪ̯.dəns] that descends from a Latin noun derived from the verb subsīdĕre.  It is a loanword from the first half of the 17th century.  Eng.  subsidence is attested already in 1607 with a meaning that is now obsolete, but by 1634 it was already being used with the meanings ‘to sink down or fall to the bottom; to precipitate’, said of suspended matter, and, said ‘of something swollen or inflated’, ‘to reduce, esp.  so as to become flat’ (OED).  Forty years later the word was being used to refer to the sinking of the ground or of buildings as well as a few others that parallel the several senses of the verb subside that we saw earlier.  This word today just has primarily those last two meanings since it most commonly refers to ‘the process by which an area of land sinks to a lower level than the land surrounding it, or a building begins to sink into the ground’ (DOCE), though it has a few other technical uses that most English dictionaries do not even mention. 

Eng.  subsidence no doubt came from French subsidence ‘sediment’.  The first attestation of French subsidence is from the mid-16th century or at least fifty years before it is first found in English.  However, the ultimate source of this word is the Latin noun subsīdĕntĭa ‘a sinking down, a settling, sediment’.  This noun was derived in a familiar way, since we have seen the process several times in this chapter.  It comes from the regular stem subsīdĕnt‑ of the present participle subsīdēns ‘sinking’ of the verb subsīdĕre ‘to sink, etc.’,  by the addition of the derivational suffix ‑ĭ‑a that creates abstract nouns (sub‑sīd‑ĕ‑nt‑ĭ‑a).  Note that there is also a variant of the English word subsidence, namely subsidency, pronounced either [sʌb.ˈsaɪ̯.dən.sɪ] or [ˈsʌb.sɪ.dən.sɪ] according to the OED.  This variant, produced with the variant ‑cy of the French ending ‑ce (see above) is now even less common than its doublet, though it is still found in a few of the more voluminous dictionaries.  Its meaning is ‘the process of subsiding, settling, or sinking’ (Chambers). 

Spanish too has borrowed this word as subsidencia, which is a highly technical term, more so than its English cognate, used primarily in geology.  The DLE gives it as a technical equivalent of hundimiento ‘sinking’ with the meaning ‘sinking of the soil, caused by the underground cavities produced by mining extractions’.  Other dictionaries do not mention mining as the only possible cause of the ground sinking and at least one dictionary, GDLEL, mentions additional uses in meteorology and medicine.  In meteorology it means ‘the lowering of a large layer of air in an anticyclonic situation’ and in medicine ‘gradual disappearance of a disease’.[4] There is little doubt that these last two senses are calques of technical uses of Eng.  subsidence, uses that do not appear in most English dictionaries due to their technical nature. 

Finally, we mentioned earlier in the section that it was unusual for a verb like subside that was presumably taken from Latin directly and not from French to be derived from the present stem, in this case subsĭd‑, and no the passive participle stem, which was subsess‑ (cf.  Chapter 8, §8.4.3.1.3).  Although at first one might have thought that the reason for this was the influence of the French word subside, which gave us Eng.  subsidy in the late 14th century, this is unlikely because of the large difference in meaning between the two words.  It is actually much more likely that the reason had something to do with the existing word subsidence in English, which had been borrowed at least fifty years before the verb subside appears in the early 17th century.  One even suspects that subside is first and foremost a back formation of the noun subsidence, and not a loan from Lat.  subsīdĕre, though this verb may have played a part on the meaning of the verb after the fact. 

[1] Note that without the length markers on the vowels, the two infinitives look identical (homographic) and, as we said earlier, chances are the two source verbs came to be confused in spoken Latin once vowel length stopped being as clearly made as it had been. 

[2]Because of the short ‑ĭ‑ in the root of the wordsubsĭdĭum, some give this word as coming from a second conjugation subsĭdēre, not from third conjugation subsīdĕre. 

[3]Sp.  subvención ultimately comes from Latin but most likely it came into Spanish from Fr.  subvention ‘financial assistance granted for relief by the State or a private or public organization’, ‘grant, subsidy’, a word that first appeared in the late 13th century, when it was spelled subvencion.  It comes from Late Latin subvĕntĭo (accusative singular: subvĕntĭōnem), a noun derived from the verb subvĕnīre ‘to support, assist, come to the aid of, rescue’, which is derived from the verb vĕnīre ‘to come’, source of Spanish patrimonial venir.  English too borrowed the word subvention from Old French in the early 15th century.  The word is rather formal and rare in Modern English, not like its Spanish counterpart, and its meaning is ‘a gift of money, usually from a government, for a special use’ (COED). 

The Latin verb rĕsĭdēre
was formed with the prefix rĕ‑ ‘back,
backwards; again’ and the verb sĕdēre
‘to sit’, using the sĭd‑ allomorph of the morpheme sĕd‑. The main meaning of
this verb was ‘to sit back’ but new senses were added through time, such as ‘to
remain sitting’, ‘to remain (behind)’, ‘to be idle, rest’, and ‘to reside’.  This
verb’s principal parts were rĕsĭdĕo, rĕsĭdēre, rĕsēdi, resessus. 

From this Latin verb come the cognates Eng.  reside ~ Sp.  residir.  Eng.  reside [ɹɪ.ˈzaɪ̯d]
is a late 15th century loanword from Middle French resider (cf.  Modern French résider
[ʀe.zi.ˈde]), itself
a late 14th century loan from Latin.  The original meaning of Eng.  reside was ‘to settle’ and ‘to take up
one’s abode or station’ though it was not commonly used with those meanings,
which are now obsolete.  The main meaning of this word today is a somewhat
formal way to say ‘to live in a place permanently or for an extended period’
(AHD), a meaning that was already present in this word by the late 16th century. 
Additionally, when speaking of a right or a quality, the verb reside means ‘to be present in or
consist of something’, as in Joe’s talent
resides in his storytelling abilities (DOCE) or The power resides on the people. 

Sp.  residir is first attested in the
late 15th century with the sense of ‘dwell permanently’ it shares with its
English cognate when the subject of the verb is a person.  This use of Sp.  residir is less formal than its English
counterpart, which is why Sp.  residir
is not always best translated by Eng.  reside
but by other less formal expressions, such as live permanently.  Thus, for instance, it is perfectly normal to say
in Spanish Mi hermano reside normalmente en
Cataluña, even in an informal oral register, whereas the English equivalent
sentence with reside, My brother usually resides in Catalonia,
sounds more formal or more appropriate to a written register.  In English, it
would be less formal or fancy to say My
brother usually lives in Catalonia or My
brother’s usual place of residence is Catalonia. ( For more on registers,
see Part I, Chapter 2,
§2.5.) 

Sp.  residir also has
the extended sense its English counterpart has in which the subject is not a
person but something else, such as a thing or an idea.  Actually, the extended
meaning goes even further in Spanish than it does in English since, again, Sp.  residir is less formal.  Thus, this sense
of residir is more likely to be
translated by the verb lie in
English, as in El problema reside en la
falta de dinero ‘The problem lies in the lack of money’. ( A synonym of this
sense of residir is radicar.)  Notice that in English, it
would sound more formal to say The
problem resides in the lack of money. 

The present participle of the Latin verb rĕsĭdēre was rĕsĭdēns, an adjective meaning ‘dwelling, residing, remaining’ (rĕ‑sĭd‑ē‑ns).  The accusative wordform
was rĕsĭdĕntem (rĕ‑sĭd‑ĕ‑nt‑em) and
the regular stem rĕsĭdĕnt‑
(rĕ‑sĭd‑ĕ‑nt‑).  The
English word resident was borrowed as
an adjective in the late 14th century from French resident ‘who resides, inhabits’, where it is already attested in
the mid-13th century, a loanword from the accusative wordform of Lat.  rĕsĭdēns (cf.  Modern French résident [ʀe.zi.ˈdɑ̃], feminine résidente
[ʀe.zi.ˈdɑ̃t]). 

By the mid-15th century, the English word resident was also being used as a noun
‘one who resides, inhabits’.  You will remember that when we discussed the
participle praesĭdens we saw
that it was common for present participles, which were primarily adjectives, to
be converted into nouns.  For more on present participles and conversion see
Part I, Chapter 8
(§8.4.3.5.3.3),
and Chapter 5
(§5.7),
respectively. 

The word resident has
acquired additional meanings over the years.  The adjective resident is used, for instance, with the meaning ‘living somewhere
in connection with duty or work’ (AHD), as in resident mechanic.  This use is quite similar in meaning to the
modifier phrase in residence, as in mechanic in residence (cf.  the
discussion of the word residence
below).  In computer science, resident
refers to a program (application) with the meaning ‘immediately available in
computer memory, rather than having to be loaded from elsewhere’ (COED).  One of
the most common uses of the noun resident
in North America (since the late 19th century), is with the meaning ‘a medical
graduate engaged in specialized practice under supervision in a hospital’
(COED) (cf.  British English houseman
or house physician). 

Sp.  residente is already attested in the
late 15th century.  This word is a good friend of Eng.  resident since it mirrors most if not all of its meanings and uses,
from the basic adjectival/substantive ‘(one) who resides, lives regularly at’,
to the ‘live at place work/duty’ sense, even the computer science and medical
senses we just mentioned.  This does not mean, however, that in all the contexts
where English, or some dialect of English, uses resident, Spanish is going to use residente, and vice versa.  This is true particularly of the noun resident.  Other alternatives or synonyms
for the noun resident are habitante ‘inhabitant’, vecino ‘neighbor’ and huésped ‘guest’, for example.  Thus,
residents of a city, district or region are typically referred to as habitantes, not residentes (English also has the paronym inhabitant, though it is less common than Sp.  habitante).  And residents of a neighborhood or condo complex or building
are typically referred to as vecinos lit. 
‘neighbors’ in Spanish rather than residentes. 
For instance, a condo’s residents’
association in Spanish is called asociación
de vecinos.  Likewise, residents of a hotel are known as huéspedes lit. ‘ guests’, never residentes (in English resident is a plausible alternative to guest). 

Likewise, the Spanish adjective residente is not always used in all the same contexts in which the English
adjective resident is found.  For
example, the use of residente meaning
‘on staff’ is not as common in Spanish.  Thus, a more common name for a resident nurse is enfermero interno, no enfermero
residente.  This is also obvious in set phrases such as resident expert, which does not have a set translation into Spanish. 
One dictionary translates the sentence He’s
our resident expert on football as Él
es el experto en fútbol de la casa, and our
resident pianist as nuestro pianista
habitual (Harrap).  Also, Spanish often prefers to use the verb residir where English would use the
adjective resident, as in Yo resido en Salem ‘I am a resident of
Salem’ for, as we saw earlier, Sp.  residir
is less formal-sounding than Eng.  reside. 

As we saw when we discussed the words president and presidence/presidency
(Sp.  presidente and presidencia), Latin regularly derived nouns
from adjective stems by means of the suffix ‑ĭ‑(a)
and, in particular it did this from present participle stems, which were
adjectives in Latin.  From the stem rĕsĭdĕnt‑
(rĕ‑sĭd‑ĕ‑nt‑) of
the present participle rĕsĭdēns, the
derived noun rĕsĭdĕntĭa
could be formed (rĕ‑sĭd‑ĕ‑nt‑ĭ‑a)
‘the act of residing; the place of residence; etc.’.  It doesn’t seem that
Classical Latin ever had a need for a noun resĭdĕntĭa
derived from the stem resĭdĕnt‑,
but the word does appear in Medieval Latin, starting in the 9th century, primarily
with the meanings ‘act of dwelling’ and ‘place of dwelling’.  From Medieval
Latin, the word passed on to French residence
in the 13th century (Modern French résidence
[ʀe.zi.ˈdɑ̃s])and from there to Middle English in the
late 14th century as residence with
the same meanings, which are also the meanings that the word has in English
today. 

The word residence is somewhat formal,
however, and not just any ‘act of dwelling’ or any ‘dwelling place’ are commonly
referred to with this word, however.  Thus, most of the time for a dwelling
place to be termed a residence, it must be a large and official one, as in the
collocations official residence and residence hall (British English hall of residence; Sp.  residencia universitaria, residencia de estudiantes or, in Spain, colegio mayor).  And for an ‘act of
dwelling’ to be considered a residence it is often one that entails a legal
permission or other official sanctioning to reside in some place, as in the
collocations residence permit and permanent residence.  In addition to
these collocations, two idiomatic phrases with this word in English are in residence and to take up residence.  The
phrase in residence means ‘committed
to live and work in a specific place, often for a certain length of time’ (AHD)
and is sometimes equivalent to the adjective resident, as in resident
painter vs. painter in residence. 
That is why in residence translates
into Spanish by the same adjective residente,
as in pintor residente.  As for the
idiom to take up residence, Spanish
equivalents are fijar la residencia
and, perhaps better yet, establecerse
or instalarse. 

In the late 16th century, English derived a doublet of the
word residence by means of the ending
‑ncy that we saw in the preceding
section, resulting in the word residency.  This word can often be
used as a synonym of residence, as in
the sense ‘legal permission to live in a country for a certain period of time’
(DOCE), but it has adopted some specialized senses as well, such as, in North
America, ‘a period of specialized medical training in a hospital; the position
of a resident’ (COED). 

Finally, the cognates Eng.  residue ~ Sp.  residuo
and their related adjectives, Eng.  residual
~ Sp.  residual, are also derived from
the same verbal stem rĕsĭd‑.
These nouns come ultimately from the Latin noun rĕsĭdŭum ‘remainder,
that which is left over/behind’, derived by conversion from the identical
neuter form of the adjective rĕsĭdŭus
‘remaining, left over/behind’ formed with the adjectival suffix ‑ŭ‑(us),
(rĕ‑sĭd‑ŭ‑us). 
Eng.  residue [ˈɹɛ.zə.ˌd(j)u] is a mid-14th
century loan from Anglo-Norman residue
and Middle French residu (Modern French
résidu [ʀe.zi.ˈdy]), which had borrowed the word from Latin earlier in
the 14th century, adapting its inflectional ending of the Latin word to the ones
expected in these varieties of French.  The main meaning of this noun is ‘a
small amount of something that remains after the main part has gone or been
taken or used’ (COED).  Sp.  residuo is first attested in the
17th century and most likely is a calque of Fr.  residu, with its own peculiar adaptation of the Latin word’s
inflection (‑um > ‑o). 

In addition to residue,
English has also borrowed the term residuum directly from Latin as a more-or-less
technical term.  The word first appears in the language in the late 17th century,
primarily as a synonym of residue, but
it was adopted later as a technical term in math and in chemistry in the 18th
century to refer to ‘that which remains after a process of combustion,
evaporation, etc..’ (OED) and in the 19th, as a term to refer ‘to persons of
the lowest class’ (OED).  At the present, the English word residuum has just those two meanings: ‘a chemical residue’ in chemistry,
and ‘a class of society that is unemployed and without privileges or
opportunities’ in sociology (COED). 

Sp.  residuo can be used much as Eng.  residue but it has some additional uses. 
In Mathematics, residuo is the word for
remainder in a calculation and plural
residuos best translates as waste or refuse, as in residuos radioactivos
‘radioactive waste’.  On the other hand, in legal terminology, Eng.  residue has a meaning that Sp.  residuo does not have, namely ‘the
remainder of a testator’s estate after all claims, debts, and bequests are
satisfied’ (AHD), also known as residuum. 
The Spanish term for this meaning is (la)
remanente (del patrimonio). 

The adjectives that accompany Eng.  residue ~ Sp.  residuo are
Eng.  residual ~ Sp.  residual.  They both contain the ‑al ending that comes from the Latin
adjectival suffix ‑āl‑(is), but these words do
not descend from a hypothetical Latin *resĭdŭālis,
which is not attested, but rather seem to have been formed in the modern languages
themselves out of Latinate (Latin-derived) word parts.  Eng.  residual
[ɹɪ.ˈzɪ.djʊ.əl] or [ɹɪ.ˈzɪ.ʤu.əl] is attested first, in the mid-16th century.  The adjective
residual today means ‘of, relating
to, or characteristic of a residue’ or ‘remaining as a residue’ (AHD). 

Curiously, there is also a noun residual in English, which arose in English around the same time as
the adjective with the meaning ‘a residual quantity’.  The noun today has additional
technical meanings such as ‘a difference between a value measured in a
scientific experiment and the theoretical or true value’ or, typically in the plural
(residuals), ‘a royalty paid to a
performer or writer for a repeat of a play, television show, or advertisement’ (COED)
(also known as repeat fees). 

The Spanish adjective residual [re.si.ˈd̪u̯al]
is typically equivalent in meaning to the English adjective residual.  Sometimes, however, it has the
‘waste’ sense that the plural noun residuos
has, as in calor residual ‘waste heat’
and aguas residuales ‘waste/sewage
water’.  The noun use of Eng.  residual
typically translates into Spanish as the noun residuo.  The ‘royalty’ sense of Eng.  plural residuals translates into Spanish as derechos de retransmisión or derechos
de redifusión.  One other difference is that the English adjective residual is more likely than its Spanish
counterpart to be used in a figurative sense, as a synonym of remaining, as in the phrase some residual decency (OSD).  Spanish would
use a different word to express this meaning, such as algunos restos/vestigios de decencia (OED). 

By the addition of the preposition/prefix prae ‘before’ to the verb sĕdēre, Latin
created the verb praesĭdēre (prae+sĕd+ē‑re). 
Its principal parts were praesĭdĕo, praesĭdēre, praesēdi/praesīdi, with
no supine/passive participle form.  As expected, the literal meaning of this
verb was ‘to sit before or in front of’ (L&S), but additional, derived
meanings were ‘to (stand) guard, watch, protect, defend’ and ‘to preside over,
manage, superintend, direct, command’ (CTL). 

This verb has given us the cognates Eng.  preside
[pɹɪ.ˈzaɪ̯d] ~ Sp.  presidir [pɾe.si.ˈd̪iɾ].  Both verbs have the same general meaning ‘be in a
position of authority in a meeting, court, etc.’ ( COED) though, as we shall
see, they are not used in the exact same way.  Eng.  preside is an intransitive verb which can be used by itself, as in Lucy always presides (at the meetings). 
If what is being presided over is mentioned, it is encoded in a prepositional
phrase with the preposition over,
such as in Lucy always presides over the
meetings.  The verb preside is more
likely to be used when speaking of leading a court session, a ceremony, or a
formal event, than a simple meeting, for instance.  For the latter the verb to chair is more likely to be used. 

Spanish presidir,
on the other hand, is a transitive verb, so that what is presided over is a
direct object, as in Lucy siempre preside
las reuniones ‘Lucy always presides over the meetings’.  Additionally, Spanish
does not have verb equivalent to Eng.  to
chair, so that Sp.  presidir can
be the equivalent of the English verb to
chair, used for less formal meetings, such as committee meetings, as well
as of the English verb to preside,
used for more formal meetings, just as juries and courts of law. 

Additionally, Sp.  presidir
can be used in ways that Eng.  preside
cannot, namely with non-human subjects.  One such meaning of presidir is ‘to occupy the most
important place in a room’, which can be said of portraits, for instance, as in
Un retrato del fundador de la fábrica
preside el despacho del director ‘A portrait of the factory’s founder
dominates/looms over the director’s office’ (Clave).  Related to that sense of
Sp.  presidir, is ‘to have great
influence or power’ or ‘to prevail’, one that is synonymous of predominar ‘to be predominant’, as in La tristeza presidió la velada ‘Sadness
prevailed/loomed over the whole evening’ (DUMM). 

These additional uses of Sp.  presidir with non-human subjects seem to be connected to the fact
that presidir in Spanish does not
entail doing anything, the way preside
does in English, and it is more about occupying a place of honor.  Thus, whereas
English dictionaries typically say that to preside
is ‘to be in control’, which suggests active participantion on the part of the
person who presides, Spanish dictionaries say that presidir is ‘to have the first or most important position’, which
suggests a rather passive role.  This interpretation of what presiding (presidir) means in Spanish explains the
extension of the verb presidir to
meanings in which the ‘presider’ is not a person and whose participation is not
an active one, as is the case with the English cognate verb. 

Although some dictionaries say that Eng.  preside comes from Latin, such as Merriam-Webster's
Collegiate and Longman DOCE, there is no doubt that English borrowed the verb preside from French présider in the early 17th century, a verb that French itself
borrowed from Latin in the late 14th century.  Sp.  presidir also makes its first appearance in the 17th century and
there is little doubt that it came in through French too.  Note that as in the
case of other derivates of Lat.  sĕdēre
in Spanish, here too, the Spanish verb is a third conjugation ‑ir verb, and not an ‑er verb, as we would have expected a
loan from a second conjugation Latin ‑ēre to be (or a first
conjugation verb as it is in French).[1]

More common than the descendants of the Latin verb praesĭdēre are the descendants of this
verb’s present participle Latin praesĭdēns,
a verbal adjective that meant ‘that sits before or in front of’ and ‘that guards,
watches, protects, defens’ (prae‑sĭd‑ē‑ns;
genitive: praesĭdĕntis;
regular stem: prae‑sĭd‑ĕ‑nt‑). 
Already in Latin this participle could be used as a noun, by conversion, with
the meaning ‘ruler, governor, leader, etc.’.  From the accusative wordform of
this noun, praesĭdĕntem,
come the cognates Eng.  president and
Sp.  presidente. 

Eng.  president
came into the language through French in the late 14th century, at first with
the meanings of ‘the appointed governor or lieutenant of a province, or
division of a country, a dependency, colony, city, etc.’  and ‘the head of a
religious house or of a college of priests; also of a hospital’ (OED). 
Additional senses were added to the word president
through time.  The sense ‘the officer in whom the executive power is vested in a
modern republic, the elected head of the government’ was first used in the
United States upon the creation of the country in the 18th century.  The word president is not used the same way in
all dialects of English, however.  In the U.S., president is ‘the title of one who presides over the proceedings of
a financial, commercial, or industrial company, as a bank, railway, mining
company, commercial trust, etc.’,  a person who in Great Britain would be called
a chairman (and in the Bank of
England and some other banks, governor)
(OED).  In Spanish too, presidente is
equivalent of Eng.  president when
referring to the leader of a state or a society, but director/a is more common when referring to the leader of a bank or
a corporation. 

Descendants of Latin participles in English and Spanish
often perform a double duty as adjectives and nouns, such as the cognates Eng.  resident ~ Sp.  residente (see next section), both of which have an adjectival use,
meaning ‘that resides’, as in the phrase resident
alien, and a noun use, meaning ‘one who resides’, as in a resident.  In the case of Eng.  president ~ Sp.  presidente, the descendants of Lat.  praesĭdēns, we find that these words are both just nouns,
not adjectives.  Another peculiarity of Sp.  presidente
is that it is one of the few nouns in ‑nte
(‑ante/‑ente), that is, words derived from Latin present participles, that
has a feminine form in ‑nta, namely presidenta ‘woman/female president’ (cf. 
Part I, Chapter 8,
§8.4.3.5.3.3). 

Latin regularly derived abstract nouns from adjective stems
by means of the suffix ‑ĭ‑a
and, in particular it did this from present participle stems which, as we have
seen, were adjectives in Latin.  Such nouns referred to the action of the verb
or some such related aspect of it.  Thus, from Latin present participle stems,
which ended in the suffix ‑nt‑, we
get nouns ending in ‑nt‑ĭ‑a. 
For example, from the stem praesĭdĕnt‑
(prae‑sĭd‑ĕ‑nt‑)
of the present participle praesĭdēns,
Latin could have formed the noun praesĭdĕntĭa
(prae‑sĭd‑ĕ‑nt‑ + ‑ĭ‑a →
praesĭdĕntĭa). 
There is no sign that Classical Latin ever did derive this word, but it is found
in Medieval Latin and from there it passed on to French as presidence and from there to English in the late 16th century. 

Because the Latin ‑nt‑ĭ‑a ending had changed to ‑nce in French patrimonial words, that is also the ending that
French gave to the borrowed word praesĭdĕntĭa
and that is also the ending that the English word presidence has.  All English words that end in ‑nce have this same source in Parisian French.  However, in English
words that came from Anglo-Norman, as opposed to Parisian French, the Latin
suffix ‑nt‑ĭ‑a had
changed to ‑ncy, for example pregnancy from pregnant and obstinacy
from obstinate.  For some reason, right
around the same time that the noun presidence
was borrowed into English from French, English created a doublet of this word
with that alternate ‑ncy ending,
namely presidency.  The former member of
the doublet has primarily the meaning ‘the action or fact of presiding’ (WNTIU)
whereas the latter means ‘the office or status of president’ (COED).  In Spanish
there is only one word, presidencia,
that is equivalent to both words.  The ending ‑cia given to this Latin borrowing is the ending that Latin words ending
in ‑t‑ĭ‑a had traditionally
adopted. 

Latin
(accusative)

‑ă‑nt‑em, ‑ĕ‑nt‑em

‑ă‑nt‑ĭ‑a, ‑ĕ‑nt‑ĭ‑a

Spanish

‑ante, ‑ente

‑ancia, ‑encia

English

‑ant, ‑ent

(1) ‑ance, ‑ence

(2) ‑ancy, ‑ency

Moving on to other words derived from the verb praesĭdēre, we find the Latin third
declension noun praesĕs,
whose genitive form was praesĭdis. 
Thus, its regular stem was prae‑sĭd‑,
just like the verb.  As an adjective, praesĕs
meant ‘presiding, protecting, guarding, defending’ and, derived from it, as a
noun, meant ‘protector, guard, guardian, defender’ (CTL).  This word has been
borrowed into English as preses or praeses (or præses), but it is quite rare.  Its
meaning is ‘the president or chairman of a meeting’, equivalent to chairman, especially in Scotland, and in
a university setting, it can mean ‘academic moderator’ (OED). 

From the stem praesĭd‑
of this word, another noun was derived in Latin by means of the suffix ‑ĭ‑um,
namely praesĭdĭum
(nominative and accusative: prae‑sĭd‑ĭ‑um;
genitive: prae‑sĭd‑ĭ‑ī; regular stem: prae‑sĭd‑ĭ‑),
which meant ‘defence, protection,
guardianship, help, aid, assistance’, ‘guard, escort, convoy’, and ‘garrison’. 
This word has given us the false-friend cognates Sp.  presidio and Eng.  presidium
and presidio. 

Modern Sp.  presidio
translates into English as prison or penitentiary.  That is not
what the word presidio meant in the 16th century, however, when this
word first entered Spanish.  Then it meant ‘military garrison attached to a town
or city’, especially those located in North Africa (Morocco), where prisoners
who committed serious crimes were often sent, but also in the Americas.  The presidios
were fortresses or fortifications (Sp.  fortaleza) in the Roman style. 

Interestingly, English
has borrowed the word presidio from Spanish to refer to Spanish garrisons
in the Americas.  Eng.  presidio means ‘a garrison, especially a fortress
of the kind established in the southwest United States by the Spanish to
protect their holdings and missions’ (AHD), as in The presidio of Rio Grande
is situated on that river (OED, 1808).  There are numerous presidios in the United
States, including thirteen in Florida, six in Texas, and five in California.  The
presidio in San Francisco, for example, is known as the Presidio Real de San
Francisco.  It was founded in 1776 and it is now part of the Golden Gate
National Recreation Area in San Francisco. 

The word presidio
is archaic in Spanish, however.  The regular words for prison are prisión,
cárcel, or penal, though penitenciaría (cognate of Eng.  penitenciary)
of is also used as a fancy synonym. ( More common than the noun penitenciaría
is the adjective penitenciario/a, which is used as the adjective for prisión,
as in the phrase reforma penitenciaria ‘prison reform’.)  From the noun presidio
(presidi‑o) the noun presidiario/a was derived by means of the Spanish
agent suffix ‑ario/a. This derived noun means ‘convict, inmate, prisoner’
(presidi‑ari‑o/a).  Derived from it is the term expresidiario ‘ex-convict,
former inmate’.[2]

The other English word derived from Latin praesĭdĭum is the
word presidium.  Its meaning is ‘any
of various permanent executive committees in Communist countries having power
to act for a larger governing body’ (AHD).  That is because the word presidium came into English in the 20th
century from Russian прези́диум (prezídium), where it had that meaning. 
Russian, of course, borrowed this word from Latin praesidium. 

[1]French borrowed second conjugation Lat.  praesĭdēre as presider,
with the ‑er infinitival ending
characteristic of first conjugation patriomonial French verbs.  In patrimonial
French words, the four Latin infinitive endings, ‑āre, ‑ēre, ‑ĕre, and ‑īre changed to ‑er, ‑oir, ‑re, and ‑ir, respectively. 

[2]This suffix comes
from the Latin suffix ‑ārĭ‑, which had two uses in Latin, just like its
Spanish descendant.  It could form first-second conjugation adjectives from
nouns and numerals (masc.  ārĭ‑us, fem.  ārĭ‑a, neut. 
ārĭ‑um).  It could also to derive nouns denoting an agent from
other nouns, which is how it is used here. 

From the Latin sitting verb sĕdēre, another verb was
derived by means of the prefix ob‑
that means ‘towards’ or ‘against’, depending on the context.  The verb was obsĭdēre, which literally meant ‘to sit
opposite to’ and whose principal parts were obsĭdĕo,
obsĭdēre, obsēdi, and obsĕssus. 
In this case too, the allomorph of the sĕd‑
root in the first two principal parts was ‑sĭd‑,
as you can see.  In the two other principal parts, the vowel was either ‑ē‑
or ‑ĕ‑, just like in the base verb sĕdēre.  In poetry, this verb
was used with the meaning ‘to sit, stay, remain, abide anywhere’ but, most
importantly, in the context of war it had the meaning ‘to hem in, beset,
besiege, blockade’ (CTL). 

The prefix ob‑ was
also added at some point to sĕdēre’s
companion verb sīdĕre,
resulting in the verb obsīdĕre,
found mostly in poetry, that also meant ‘to beset, besiege, blockade’ and ‘to
occupy, take possession of’ (L&S) and thus could be a synonym of obsĭdēre.  The only two attested
principal parts of this verb are obsīdō
and obsīdĕre. 

Finally, we should mention that there is a related deponent
verb obsĭdĭāri ‘to lie in wait for,
to waylay’ (principal parts: obsĭdĭor,
obsĭdĭāri).  A deponent verb is one
that has passive forms but active meanings (cf.  Part I, Chapter 8,
§8.4.3.4). 
This verb is not attested until fairly late, in the post-Augustan period. 

From the verb obsĭdēre,
Latin derived two synonymous nouns: obsĭdĭum and obsĭdĭo, both of which meant ‘siege, blockade’.  It isn’t clear
what the difference in meaning between the two was, if any, or whether they
were used at different times or in different places.  We saw the first of these words
when we saw that Sp.  asedio, one of the two words for
‘siege’, is said to derive from the noun obsĭdĭum
(ob‑sĭd‑ĭum).Presumably asedio was a
patrimonial word, given the ĭ to e sound change, but the change in
the prefix’s vowel from o to a is not at all common.  This Latin noun
was derived from the present stem of the verb, ob‑sĭd‑ and the suffix ‑ĭ‑um, used at one time form abstract
nouns. 

Regarding the word obsĭdĭo, its genitive wordform was obsĭdĭōnis and thus its regular stem was ob‑sĭd‑ĭōn‑. The derivational ending of this
word looks just like the suffix ‑ĭōn‑
that we have seen so often that derives third-declension abstract nouns from
verbs (‑ĭo in the nominative case), but there is a major
difference.  In this case, this suffix attaches itself not to the passive
participle (supine) stem of the verb, obsĕss‑,
but rather to the present stem, in this case obsĭd‑. There are very few examples of abstract nouns
derived by means of this suffix from the present stem of a verb.  Two of them
are lĕgĭo-lĕgĭōnis ‘legion’ and rĕgĭo-rĕgĭōnis ‘region’.[1]

However, as we will see below, there is also a noun that is
derived from the passive participle stem by means of the suffix ‑ĭōn‑, namely obsĕssĭo (gen.  obsĕssĭōnis;
regular stem: ob‑sĕss‑ĭōn‑).  No
doubt, you will recognize the cognates Eng.  obsession
~ Sp.  obsesión as coming from that
derived noun.  But before turning to Eng.  obsession
~ Sp.  obsesión, let us mention that
English did borrow at one point, in the middle of the 15th century, the noun obsidion‘siege’, through French, where it was a
learned loanword from Latin obsĭdĭo-obsĭdĭōnis.  Its use was rare even then and the
word is now obsolete. 

In addition
to the nounobsidion, English also borrowed from French
an adjective derived from the noun.  The English adjective was obsidional
‘pertaining to a siege’, borrowed in the 16th century from French obsidional, itself borrowed in the 15th
century from Lat.  obsĭdĭōnālis, an adjective derivedby means of the third declension
adjectival suffix ‑āl‑ (ob‑sĭd‑ĭōn‑āl‑is).  There is even a synonym of obsidional that was created in English
in the late 19th century, namely obsidionary, formed from obsidion and the Latinate suffix ‑ary that we saw in the previous section. 

There is
another, related adjective in English, namely obsidious ‘besieging; besetting’.  According to the OED, this adjective
was created in the early 17th century, in English, out of the Latin noun obsĭdĭum that gave us Sp.  asedio by the addition of the Latinate
suffix ‑ous (from Lat.  ‑ōs‑) that formed first/second declension adjectives
from nouns.  Few English dictionaries mention this adjective and the few that do
mention that it is rare.  However, for some reason, just as in the case of the
other English words containing the same stem, none of dictionaries says this
word is either archaic or obsolete. 

Although the word obsidion
and its relatives will not be familiar to most speakers of English, they will
probably remind many speakers of a much more common word, namely obsidian,
which refers to ‘a hard, dark, glass-like volcanic rock formed by the rapid
solidification of lava without crystallization’ (COED). ( Every time I type the
word obsidion, Word replaces it with
the word obsidian.)  There is no
connection between the two words, however.  Eng.  obsidian (Sp.  obsidiana)
is a 17th century loanword from Latin, but its form, what makes it look like
the noun obsidion, is actually due to
a a misreading that a copyist made at some point when transcribing the Latin
word into Latin.  The actual, original Latin word was obsĭānus, not obsĭdĭānus,
an adjective derived from Obsĭus,
a Roman surname and, according to Pliny the Elder, the name of the person who
first discovered or described this type of stone in Ethiopia (Obsĭ‑us +‑ān‑
→ obsĭ‑ān‑us).[2]

Let us return now to the cognates Eng.  obsession [əb.ˈsɛ.ʃən] ~ Sp.  obsesión[ob.se.ˈsi̯on].  These words are
loanwords ultimately from Lat.  obsessĭo,
a noun derived from the stem obsess‑
of the passive participle obsessus of
the verb obsĭdēre by means of the
noun-forming suffix ‑ĭōn‑ (genitive case: obsessĭōnis; regular stem: ob‑sess‑ĭōn‑).  Curiously, in Latin this
word was a synonym of obsĭdĭo-obsĭdĭōnis and obsĭdĭum, and thus meant ‘siege, blockade’.  That was also the meaning the
word obsession had when this word was
borrowed into English in the early 16th century from French, which itself had
borrowed it from Latin in the 15th century.  However, by 1590, the French word
had come to mean ‘state or condition of someone besieged by a demon’, a
preliminary stage to demonic possession, but without the demon actually
inhabiting the body.  That meaning was transferred to the English cognate soon
thereafter. 

To understand the original meaning of Lat.  obsessĭo, and its companion possessĭo, it
helps to understand how these words were
used in Roman military terminology.  In Roman warfare, there were two stages of
taking over an enemy city.  The first one was obsession (obsĭdēre, obsessĭo), the siege, and the second one
possession, or taking it over by
force after the walls have been breached.  In the next section we will explore the
word possession and the verb possĭdēre that this noun is derived from,
since these words, which are actually compounds, are also derived from the verb
sĕdēre and also contains
the root sĕd‑.[i]

The words obsession
and possession are used in Christian terminology
to refer to supposed demonic influences on people but, obviolsy, they are mere analogues
of the Roman war terms we just saw.  In obsession, a demon besieges a person and
in possession the demon takes over the person.  By the late 17th century the
word obsession was being used in
non-religious contexts to refer to anything that absorbs a person’s mind.  In
Modern English, the word obsession has
lost the military and religious senses and can be defined as ‘an extreme
unhealthy interest in something or worry about something, which stops you from
thinking about anything else’ (DOCE) or, with more of a psychological twist, as
a ‘compulsive preoccupation with a fixed idea or an unwanted feeling or
emotion, often accompanied by symptoms of anxiety’ (AHD). 

Sp.  obsesión first
appeared in the DRAE’s 1780 edition of the DRAE.  It is obviously a loanword, which
probably came into the language through French, just like its English cognate
did, not directly from Latin.  The borrowing probably took place after the
meaning had already changed to its current one in the late 17th century, for
there is no sign that the Spanish word obsesión
ever meant anything other than what it means today, which is also exactly what
it means in Modern French and Modern English. 

These cognates that come from Lat.  obsessĭo have a more technical use in the field of psychology and
psychiatry in the modern languages, one which can be defined as follows:

An obsession is the inability of a person to stop thinking
about a particular topic or feeling a certain emotion without a high amount of
anxiety.  When obsessed, an individual continues the obsession in order to avoid
the consequent anxiety.  In the case of obsessive compulsive disorder (OCD), the
individual may have only the obsessions, compulsions or both.  An example of an
obsession in OCD is a person who can't stop thinking about dirt or germs that
they could come into contact with.  In this case, thinking about the dirt and/or
germs is the obsession.[ii]

English synonyms of the word obsession are preoccupation,
fixation, compulsion, and mania. 
Spanish synonyms of obsesión are manía, fijación, and obcecación. 
The first two are cognates of Eng.  mania
and fixation, respectively.  In Spanish
colloquial speech, perra and neura are common synonyms, at least in
some dialects (Clave). 

Both English and Spanish have words related to or even
derived from the nouns Eng.  obsession
~ Sp.  obsesión.  One pair of words that
the two languages have in common are the cognate adjectives Eng.  obsessive
[əb.ˈsɛ.sɪv] ~ Sp.  obsesivo/a [ob.se.ˈsi.βo].  The word *obsessīvus
did not exist in Latin, though it could have existed, since it is properly formed
by the addition of the first-second conjugation adjectival suffix ‑īv‑
to perfect passive participial stems of verbs.  But we know that these
adjectives were created in the field of psychology in the early 20th century, in
one of the modern languages and then copied in the others, out of the stem obsess‑ of the word obsession and the Latinate suffix Eng.  ‑ive (in French, it is masc.  ‑if,
fem.  ‑ive; in Spanish,‑ivo/a).  Its main meaning is ‘of,
relating to, characteristic of, or causing an obsession’ (AHD).  From this
adjective, English has derived the adverb obsessively (Sp.  obsesivamente)
by the addition of the native (Germanic) suffix ‑ly and the noun obsessiveness, by the addition of
the native suffix ‑ness (there is no
Spanish equivalent for this latter word, though *obsesividad would be a likely candidate). 

Let us look now at the verbs related to these nouns.  English
has borrowed the Latin verb obsĭdēre not
once but twice.  A failed attempt was the borrowing as by some author in the
late 17th century of this verb as obside,
with the meaning ‘to beset, invest, surround, encompass’ (OED).  Needless to
say, the verb is now obsolete.  But before that failed attempt, English had
already borrowed the same verb in the early 16th century, from the usual
source, namely the verb’s passive participle, the verb form obsessus, resulting in the verb obsess.  When the verb was first borrowed
it had the expected meaning, namely ‘to besiege a fortress’.  By the mid-16th
century the verb had already acquired the sense of a demon besieging a person,
much like the noun obsession had
changed meanings.  By the 17th century, the past participle of this verb, obsessed, had already become an
adjective with the meaning ‘haunted, tormented by an evil spirit’.  Then, in the
20th century, the verb acquired its modern transitive and intransitive meanings
related to being constantly preoccupied with something. 

Dictionaries tell us that the verb obsess has a transitive meaning, ‘to preoccupy the mind of
excessively’, and an intransitive one, derived from the former, ‘to have the
mind excessively preoccupied with a single emotion or topic’ (AHD).  The latter
is indeed a use of the verb obsess,
as in as in She always obsesses about her
hair, though this use is rare.  But English obsess is not really used transitively anymore and what
dictionaries term as the passive use of the transitive verb (be/become/get obsessed by) is really an
adjectival use of obsessed, the past
participle of the verb, not a true passive participle, as shown by the fact that
the source of the obsession is typically coded with a with-phrase and not a by-phrase,
as in She is obsessed with her hair.  Note
that the transitive sentence Her hair obsesses
her sounds a bit odd and is of dubious grammaticality. 

The equivalent of Eng.  obsess
in French is obséder, which was
borrowed and adapted from Lat.  obsĭdēre. 
Spanish, on the other hand, never borrowed this Latin verb.  Instead, it created
a verb obsesionar out of the noun obsession (obsesion‑ar).  The verb was created by some unknown author sometime in
the second half of the 19th century, but it did not appear in a dictionary
until 1917, and in the DRAE until 1927, after which time it becomes very common
in the language. 

Spanish obsesionar
is equivalent to transitive English obsess,
meaning something like ‘to cause an obsession’.  The difference is that this verb is indeed used as a transitive verb,
as in Lo obsesiona el fútbol (or El fútbol lo obsesiona) ‘He’s obsessed with
soccer’. As usual, this transitive verb
can be used ‘pronominally’ (reflexively), as obsesionarse (por/con), which translates as to get obsessed (by/with/about), as in Se obsesiona por/con cualquier cosa ‘He becomes obsessed with just about
anything’.  Spanish also uses the past participle of this verb, obsesionado/a, as an adjective in constructions
such as estar obsesionado/a (con), as
in Está obsesionada con salir a comer
‘She’s obsessed about going out to eat’. 

[2] Pliny the Elder (23-79 CE), whose Roman name
was Gaius Plinius Secundus, wrote about this in his famous Naturalis Historia (Natural History), the first encyclopedia ever
written.  In this book he mentioned that “Among the various kinds of glass, we
may also reckon Obsian glass, a substance very similar to the stone which
Obsius discovered in Æthiopia.  The stone is of a very dark colour, and
sometimes transparent; but it is dull to the sight,…” (Chapter 67: “Obsian
glass and obsian stone”).