Question: When did the Portuguese language develop?

History of Portuguese

The Portuguese language developed in the Western Iberian Peninsula from Latin spoken by Roman soldiers and colonists starting in the 3rd century BC. Old Portuguese, also known as Galician-Portuguese, began to diverge from other Romance languages after the fall of the Western Roman Empire and the Germanic invasions, also known as barbarian invasions in the 5th century and started appearing in written documents around the 9th century. By the 13th century, Galician-Portuguese had become a mature language with its own literature and began to split into two languages. However, the debate of whether Galician and Portuguese are nowadays varieties of the same language, much like American English or British English, is still present. In all aspects—phonology, morphology, lexicon and syntax—Portuguese is essentially the result of an organic evolution of Vulgar Latin with some influences from other languages, namely the native Gallaecian and Lusitanian languages spoken prior to the Roman domination.
Social history
Romanization

Arriving on the Iberian Peninsula in 218 BC, the ancient Romans brought with them Latin, from which all Romance languages descend. The language was spread by arriving Roman soldiers, settlers and merchants, who built Roman cities mostly near the settlements of previous civilizations. Later, the inhabitants of the cities of Lusitania and the rest of Romanized Iberia were recognized as citizens of Rome.
Roman control of the western part of Hispania was not consolidated until the campaigns of Augustus in 26 BC. Although the western territories to the south of the Tagus River were only conquered after the victory of Licinius Crassus in the year 93 BC,[1] only an estimated four hundred words of the native languages[2] persist in modern Portuguese. After 200 years of wars first with the Carthaginians in the Eastern part of the peninsula, and then the local inhabitants, emperor Augustus conquered the whole peninsula, which was named Hispania. He then divided it into three provinces, Hispania Tarraconensis, Hispania Baetica, and Lusitania, the latter of which included most of modern Portugal. In the 3rd century, emperor Diocletian split Tarraconensis into three, creating the adjacent province of Gallaecia, which geographically enclosed the remaining part of Portugal, and modern-day Galicia (in the northwestern region of Spain).
Iberian Romance

Between AD 409 and 711, as the Roman Empire was collapsing, the Iberian Peninsula was invaded by peoples of Germanic origin, known by the Romans as Barbarians. The Barbarians (mainly Suevi and Visigoths) largely absorbed the Roman culture and language of the peninsula; however, since the Roman schools and administration were closed and Europe entered the Early Middle Ages, the Vulgar Latin language of ordinary people was left free to evolve on its own and the uniformity of the language across the Iberian Peninsula broke down. In the north-western part of the Peninsula (today's Northern Portugal and Galicia), Vulgar Latin began gaining a growing number of local characteristics, leading to the formation of what linguists today call Galician-Portuguese. The Germanic languages influenced Galician-Portuguese by introducing words often linked to the military like guerra (war) or laverca (lark), placenames such as (Resende), animals like ganso (goose), texugo (badger), human feelings such as orgulho (pride), verbs like brigar (to fight), suffixes like reguengo (royal domain) and everyday objects such as frasco (flask).
From 711, with the Moorish invasion of the Iberian Peninsula, Arabic was adopted as the administrative language in the conquered regions. However, much of the population continued to speak the Latin-derived Romance dialects, called collectively by modern linguists Mozarabic. The main effect of the Arabic influence was lexical. Modern Portuguese has between 400 up to as much as 800 words of Arabic origin[3] (many were absorbed indirectly through Mozarabic) especially relating to food, agriculture and the crafts, which have no cognates in other Romance languages except in Spanish from which in fact, Portuguese borrowed many of its Arabic-derived words. The Arabic influence is also visible in placenames, especially in the southern provinces, such as the Algarve, Alfama and Fátima.
However, there are no Arabic loan words in the lexicon related to human feelings or emotions; those are all of Latin, Germanic or Celtic origin.
Proto-Portuguese




























Excerpt of medieval
Portuguese poetry[4]Das que vejonon desejooutra senhor se vós non,e desejotan sobejo,mataria um leon,senhor do meu coraçon:fin roseta,bela sobre toda fror,fin roseta,non me metaen tal coita voss'amor!João de Lobeira
(1270?–1330?)
The oldest surviving records containing written Galician-Portuguese are documents from the 9th century. In these official documents, bits of Galician-Portuguese found its way into texts that were written in Latin. Today, this phase is known as "Proto-Portuguese" simply because the earliest of these documents are from the former County of Portugal, although Portuguese and Galician were still a single language. This period lasted until the 12th century.
The lyric period
What modern scholars call Galician-Portuguese was originally the native language of the medieval Kingdom of Galicia, which was founded in 410 and included the northern part of present-day Portugal. It appears to have also been used regularly in other Christian kingdoms of the Iberian Peninsula as the language for lyric song. It was employed by poets from throughout the non-Basque medieval Christian kingdoms of the peninsula; including Leonese, Castilian, Aragonese and Catalan. It is also the language used in the Cantigas de Santa Maria. These songs were traditionally attributed to Alfonso X, a Castilian king, though more recent work shows that they must have been composed in collaboration with many translators, poets and musicians.
The divergence of Galician-Portuguese
Portugal was formally recognized as an independent kingdom in 1143 by the Kingdom of León, into which Galicia was incorporated at the time, with Afonso Henriques as its first king. In 1290, King Diniz created the first Portuguese University in Lisbon (the Estudo Geral) and decreed that the language of the Portuguese, then simply called the "Vulgar language" (i.e. Vulgar Latin) should be used in preference to Latin and known as the "Portuguese language". In 1296, Portuguese was adopted by the Royal Chancellary and was used not only in poetry but also when writing law and in notaries. In the first period of "Old Portuguese" (from 12th to the 14th century), the language came gradually to be used in official documents. With the political separation of the County of Portugal from Galicia, Galician-Portuguese lost its unity and slowly became two increasingly distinct languages. This growing difference accelerated when Galicia became part of Castile and Galician was increasingly influenced by Castilian. Meanwhile, the southern variant of Galician-Portuguese became the modern Portuguese language within the Kingdom of Portugal and its empire.
Standardization during the Renaissance

The end of "Old Portuguese" was marked by the publication of the Cancioneiro Geral by Garcia de Resende, in 1516.
"Modern Portuguese" developed from the early 16th century to the present. During the Renaissance, scholars and writers borrowed many words from classical Latin (learned words borrowed from Latin also came from Renaissance Latin) and ancient Greek, which increased the complexity of the Portuguese lexicon. Most literate Portuguese speakers were also literate in Latin; and thus they easily adopted Latin words into their writing—and eventually speech—in Portuguese. As with most European vernacular languages, the standardization of the Portuguese language was propelled by the development of the printing press. In 1536 Fernão de Oliveira published his Grammatica da lingoagem portuguesa in Lisbon, the first Portuguese grammar.[5][6] The work of this heterodox Dominican priest, philologist and mariner was soon followed. In 1540, João de Barros crown officer published his Gramática da Língua Portuguesa along with moral dialogues and basics of the Catholic Church to help teaching young aristocrats.[6][7] This second work, illustrated with woodcuts, is considered the world's first printed illustrated text book.[7]
Expansion during the age of discovery

The second period of Old Portuguese covers the time from the 14th to the 16th centuries and is marked by the Portuguese discoveries of the 15th and 16th centuries. In that time, colonisers, traders and missionaries spread the Portuguese language to many regions in Africa, Asia and The Americas. Today most Portuguese speakers live in Brazil, the biggest former colony of Portugal. By the mid-16th century, Portuguese had become a lingua franca in Asia and Africa, used not only for colonial administration and trade but also for communication between local officials and Europeans of all nationalities. In Ceylon (modern Sri Lanka) several kings became fluent speakers of Portuguese, and nobles often took Portuguese names. The spread of the language was helped by its association with the Catholic missionary efforts, which led to its being called Cristão ("Christian") in many places. The Nippo Jisho, a Japanese–Portuguese dictionary written in 1603, was a product of Jesuit missionary activity in Japan. The language continued to be popular in parts of Asia until the 19th century, despite the severe measures taken by the Dutch to abolish it in Ceylon and Indonesia.
Some Portuguese-speaking Christian communities in India, Sri Lanka, Malaysia and Indonesia preserved their language even after they were isolated from Portugal. The language has largely changed in these communities and has evolved through the centuries into several Portuguese creoles. Also, a considerable number of words of Portuguese origin are found in Tetum, the national language of East Timor, such as lee "to read" (from ler), aprende "to learn" (from aprender) and tenke "to have to" (from tem que). Portuguese words entered the lexicons of many other languages, such as pan "bread" (from pão) in Japanese (see Japanese words of Portuguese origin), sepatu "shoe" (from sapato) in Indonesian, keju "cheese" (from queijo) in Malay and meza "table" (from mesa) in Swahili.  Due to the vast expanse of the Portuguese Empire, there are also numerous words that entered English (see: List of English words of Portuguese origin) such as albino, baroque, mosquito, potato, savvy and zebra.
Historical sound changes

Both in morphology and in syntax, Portuguese represents an organic transformation of Latin without the direct intervention of any foreign language. The sounds, grammatical forms, and syntactical types, with a few exceptions, are derived from Latin, and almost 80% of its vocabulary is still derived from the language of Rome. Some of the changes began during the Empire, others took place later. A few words remained virtually unchanged, like carro, taberna ("tavern"), or even returned to a form close to the original, such as coxa ("thigh") – in this case, however, only the spelling looks identical: Latin ⟨x⟩ and Portuguese ⟨x⟩ designate two completely different sounds, [ks] and [ʃ] respectively.
Learned Latinisms were formed in the late Middle Ages, due to the use of Church Latin by the Catholic Church, and during the Renaissance, when Classical antiquity in general, and Literary Latin in particular, enjoyed great prestige. Thus, for example, Latin aurum, which had originated ouro ("gold") and dourado ("golden"), was re-introduced as the adjective áureo ("golden"). In the same way, locālem ("place"), which had evolved to lugar, was later reintroduced as the more erudite local. Many erudite Greek words and combining elements were also introduced or reintroduced in this way. Because of this, many Latin words are still familiar to Portuguese speakers.
The letter ⟨v⟩ was the vowel we know today as ⟨u⟩, and ⟨c⟩ was always pronounced [k], so centum was originally pronounced [ˈkentũ]. Later Latinisms are marked with (L).
Palatalization
Palatalization of voiceless stops—the consonants [k] and [t] assimilated with the high vowels [e] and [i], and with the semivowel [j].
centum > [tj]ento > [ts]ento > [s]ento (hundred)
facere > fa[tj]ere > fa[ts]er > fa[dz]er > fa[z]er (to do)
A more ancient evolution was 
fortiam > for[ts]a > for[s]a (strength)
Voicing
Voicing—some consonants did not disappear but rather evolved with voiceless stops becoming voiced stops and voiced stops becoming voiced fricatives in certain positions, a common type of sound change:
mūtum > mudo (mute)
lacum > lago (lake)
locustam > lagosta (lobster)
Lenition
Lenition—consonant clusters, especially long (geminate) consonants, were simplified:
guttam > gota (drop)
quatturo > quatro (four)
peccāre > pecar (to sin)
Phoneme [b] evolved as [v]. The /v/ phoneme was generally derived either (1) from an allophone of Latin /b/ between vowels or (2) from the Latin phoneme corresponding to the letter ⟨v⟩ (pronounced [w] in Classical Latin, but later fortified to the status of a fricative consonant in Vulgar Latin). 
habēre > haver
fabam > fava (broad bean)
amābam/amābat > amava
līber, lībri > livro
parabola > palavra
Elision
Elision—the consonants [l] and [n] of Vulgar Latin were deleted between vowels, after which sometimes the vowels around them coalesced, or an epenthetic semivowel was introduced between them. Original geminates [ll], [nn] persisted, later becoming single [l], [n].
dolōrem > door > dor (pain); (L) doloroso (painful)
bonum > bõo > bom (good)
ānellum > ãelo > elo (bond); (L) anel (ring)
salīre > sair (to get out)
cōlāre > coar (sift)
notulam > nódoa (stain)
catēnam > cadeia (jail, chain); (L) cadena (jail, chain) (more erudite)
Palatalization
Palatalization of liquids and nasals—the consonants [l] and [n] assimilated with the semivowel [j], producing the palatals lh [ʎ] and nh [ɲ]: 
mulierem > mulher (woman)
iūnium > junho (June)
Nasalization
In medieval Galician-Portuguese, /m/ and /n/ between vowels or at the end of a syllable became the velar nasal phoneme /ŋ/, leading to regressive nasalization of the preceding vowel as a secondary phonetic effect.[8] This consonant was then at a later stage lost or modified in Portuguese, although it was retained in Galician in some words (e.g. modern unha (/uŋa/) identical in pronunciation to medieval hũa).
This change produced one of the most striking phonological differences between Portuguese and Spanish. The history of nasal vowels in hiatus with a previous or following vowel is complex, depending on the identity of the two vowels and the position of the stress.
1. If the vowels were near each other, they collapsed into a single vowel (nasal or oral, according to the nasality of the stressed vowel):
bonum > bõo > bom (good masc.)
calentem > caẽte > quente (hot)
ganātum > gãado > gado (cattle)
lānam > lãa > lã (wool)
2. Otherwise, if the second vowel was more closed, the result was usually a nasal diphthong:
manum > mão (hand)
canem > cães (dogs)
3. If the second vowel was more open, or as open, nasalization was lost:
lūnam > lũa > lua (moon). Exception: ūnam > ũa > uma (one)
bonam > bõa > boa (good fem.)
plēnum > chẽo > cheio (full); (L) pleno (full)
4. If the first vowel was [i], however, nasalization evolved to a palatal nasal consonant, inserted between the two vowels:
vīnum > vĩo > vinho (wine)
rēgīnam > *ragina > raĩa > rainha (queen)
Progressive nasalization—The spread of nasalization forward from a nasal consonant, especially [m]. 
mātrem > made > mai > mãe (mother)
meam > mia > mĩa > minha (my fem.); but compare meum > meu (my masc.)
ad noctem > anoite > ãote > ontem [ˈõtẽĩ] (yesterday).
Epenthesis
Epenthesis—the insertion of a sound to break up a combination of vowels which was difficult to pronounce: 
harēnam > arẽa > areia (sand); (L) arena (arena)
gallīnam > galĩa > galinha (chicken)
vīnum > vĩo > vinho (wine)
Examples such as the former two have been used by some authors to argue that the digraph nh was a nasal approximant in medieval Portuguese, and thus its pronunciation [j̃] in most dialects of Brazil and São Tomé and Príncipe is the original one.[9]
Dissimilation
Dissimilation—Modification of a sound by the influence of neighbouring sounds; similar became different over time, so as to ease pronunciation.
1. Between vowels:
locustam > lagosta (lobster)
campanam > campãa > campa (tomb)
2. Between consonants:
memorāre > nembrar > lembrar (to remember); (L) memorizar (to memorize)
animam > alma (soul); (L) animado (animated)
locālem > logar > lugar; (L) local (place)
Metathesis
Metathesis—a sound change that alters the order of phonemes in a word. 
Semi-vowel metathesis: 
prīmārium > primeiro (first); (L) primário (primary)
Consonant metathesis in [l] and [ɾ]: 
tenebrās > tẽevras > trevas (darkness); this was rare in Portuguese; (L) tenebroso (dark)
Vowel metathesis: 
genuculum > *genoclo > gẽolho > joelho (knee)
Medieval sound changes

Old Portuguese had seven sibilants: lamino-alveolar affricates /ts/ (⟨c⟩ before ⟨e/i⟩, ⟨ç⟩ elsewhere) and /dz/ (⟨z⟩); apico-alveolar fricatives /s/ (⟨s⟩, or ⟨ss⟩ between vowels) and /z/ (⟨s⟩ between vowels); palato-alveolar fricatives /ʃ/ (⟨x⟩) and /ʒ/, earlier /dʒ/ (⟨j⟩, also ⟨g⟩ before ⟨e/i⟩); and palato-alveolar affricate /tʃ/ (⟨ch⟩). This system was identical to the system of Old Spanish, and Portuguese followed the same path as Old Spanish in deaffricating the sibilants /ts/ and /dz/ into lamino-alveolar fricatives that still remained distinct from the apico-alveolar consonants. This produced a system of six fricatives and one affricate, which is still maintained in small parts of northeast Portuguese province of Trás-os-Montes and in the adjacent Mirandese language; but in most places, these seven sounds have been reduced to four.
Everywhere except in the above-mentioned parts of Trás-os-Montes, the lamino-alveolar and apico-alveolar fricatives merged. (This appears to have happened no earlier than the seventeenth century, on the evidence of the spelling system used by Alexandre de Rhodes to represent Middle Vietnamese). In northern Portugal and Galicia, they became apico-alveolars (as in the central and northern peninsular Spanish pronunciation of /s/). In most of Brazil, they became lamino-alveolar consonants (as in the English pronunciation of /s/ and /z/). In central and southern Portugal (and in Rio de Janeiro and surrounding areas, due to the relocation of the Portuguese nobility in the early 1800s), they merged as lamino-alveolars before vowels, but as palato-alveolar /ʃ ʒ/ elsewhere. Meanwhile, /tʃ/ eventually lost its affrication and merged with /ʃ/, although /tʃ/ is maintained throughout Trás-os-Montes.
It appears that the sound written ⟨v⟩ was at one point during the medieval period pronounced as a voiced bilabial fricative [β]. Subsequently, it either changed into a labiodental fricative [v] (as in central and southern Portugal, and hence in Brazil), or merged into /b/ (as in northern Portugal and Galicia, similarly to modern Spanish). Also similarly to modern Spanish, the voiced stops /b d ɡ/ eventually became pronounced as fricatives [β ð ɣ] between vowels and after consonants, other than in the clusters /nd/ /ld/ /nɡ/ /mb/ (the nasals were presumably still pronounced in these clusters, rather than simply reflected as a nasal vowel). However, this change happened after the colonization of Brazil, and never affected Brazilian Portuguese.
Final unstressed /a/ was subsequently raised to /ɐ/. Final /o/ was eventually raised to /u/ in both Portugal and Brazil, but independently. Final unstressed /e/ was likewise raised to /i/ in Brazil, but shifted to /ɨ/ in Portugal (now barely pronounced). In Portugal (but not in Brazil), these changes have come to affect almost all unstressed instances of /a/ /o/ /e/; but not /ou/ (which now appears as /o/), nor the former sequences /aa/ /ee/ /oo/ (which now appear as /a/ /ɛ/ /ɔ/ respectively), nor in syllables closed by stop consonants (e.g. in secção "section", optar "to choose"). Hence in Portugal pesar "to weigh" /pɨzaɾ/ but pregar "to preach" /prɛɡaɾ/ (former preegar < praedicāre); morar "to live" /muɾaɾ/, but corado "blushing" /kɔɾadu/ (former coorado < colōrātum), roubar "to rob" /ʁobaɾ/. (In Brazil these appear as /pezax/, /preɡax/, /moɾax/, /koɾadu/, /xo(u)bax/.) Recently in Rio de Janeiro (and rapidly spreading to other parts of Brazil), /t/ and /d/ have been affricated to /tʃ/ and /dʒ/ before /i/, including /i/ from unstressed /e/.
Old Portuguese had a large number of occurrences of hiatus (two vowels next to each other with no consonant in between), as a result of the loss of Latin /l n d ɡ/ between vowels. In the transition to modern Portuguese, these were resolved in a complex but largely regular fashion, either remaining, compressing into a single vowel, turning into a diphthong, or gaining an epenthetic consonant such as /v/ or /ɲ/; see above.
Portuguese traditionally had two alveolar rhotic consonants, a flap /ɾ/ and trill /r/, as in Spanish. In most areas of Portugal the trill /r/ has passed into a uvular fricative /ʁ/. In most parts of Brazil, however, /r/ has become an unvoiced fricative /x/ (variously [x χ h]), and all instances of /ɾ/ not preceding a vowel have been likewise affected. (When final, this sound is sometimes not pronounced at all.)
/l/ at the end of a syllable became heavily velarized /ɫ/ in Portuguese. This still remains in Portugal, but in Brazil has progressed further, merging into /w/.
See also
Differences between Spanish and Portuguese
Galician language
History of Galicia
History of Portugal
History of Brazil
List of English words of Portuguese origin
Portuguese vocabulary
Romance languages
Spelling reforms of Portuguese
Museum of the Portuguese Language
Portuguese Language Orthographic Agreement of 1990