# Phonological history of Hindustani

The inherited, native lexicon of the Hindustani language exhibits a large number of extensive sound changes from its Middle Indo-Aryan and Old Indo-Aryan. Many sound changes are shared in common with other Indo-Aryan languages such as Marathi, Punjabi, and Bengali.

## Indo-Aryan etymologizing

The history of Hindustani language is marked by a large number of borrowings at all stages. Native grammarians have devised a set of etymological classes for modern Indo-Aryan vocabulary:
* Tadbhava (Sanskrit: तद्भव, "arising from that") refers to terms that are inherited from vernacular Apabhraṃśa (Sanskrit: अपभ्रंश, "corrupted"), from the dramatic Prakrits, and further from Sanskrit. An example is Hindustani jībh "tongue", inherited through Prakrit jibbhā, from Sanskrit jihvā. Such words are the focus of this article.
* Tatsama (Sanskrit: तत्सम, "same as that") refers to words that are borrowed into Hindi or Old Hindi directly from Sanskrit with minor phonological modification (e.g. lack of pronunciation of the final schwa). The Hindi register of Hindustani is associated with a large number of tatsama words through Sanskritisation. An example is Hindustani jihvāmūlīy "guttural", directly from Sanskrit jihvāmūlīya.
* Ardhatatsama (Sanskrit: अर्धतत्सम, "half-same as that") refers to words that are semi-learned borrowings from Sanskrit. That is, words that underwent some tadbhava sound changes, but were adapted on the basis of a Sanskrit word. An example is Hindustani sūraj "sun", which is from Prakrit sujja, from Sanskrit sūrya. We would expect Hindustani *sūj from Prakrit, but the -r- was added later on after the Sanskrit word. Such adaptation to Sanskrit occurred continuously and as early as the Middle Indo-Aryan stage. Adapted words were crucial to determining the date and chronology of sound changes.
* Deśaj (Sanskrit: देशज, "indigenous") refers to words that may or may not be derived from Prakrit, but cannot be shown to have a clear Sanskrit etymon. This is sometimes complicated by Sanskrit re-borrowing of Prakrit words. Such words sometimes derive from Non-Indo-Aryan languages—primarily Austroasiatic (Munda) languages, as well as Dravidian and Tibeto-Burman languages. An example is Hindustani ōṛhnā "to cover up, veil", from Prakrit ǒḍḍhaṇa "covering, cloak", from Dravidian, whence Tamil உடு (uṭu, "to wear").
In the context of Hindustani, other etymological classes of relevance are:
* Perso-Arabic loanwords, which came to Old Hindi from Classical Persian. The pronunciation is closer to Classical Persian, rather than modern Iranian Persian. The Urdu register of Hindustani is associated with a large number of Perso-Arabic loanwords. An example is Hindustani zubān "tongue, language", from Classical Persian zubān (whence Persian zobân).
* Borrowings from Northwestern Indo-Aryan. Modern Hindustani, while based primarily on the language of the Khariboli region, comes from a dialectal mixture. Many of the Western Hindi dialects are transitional to Punjabi and the Northwestern Indo-Aryan languages, and have donated words to Hindustani that underwent Northwestern sound changes. We often encounter doublets like Hindustani makkhan "butter", borrowed from Northwestern dialects (compare Punjabi makkhaṇ), and Hindustani mākhan, the native tadbhava term which is now archaic/obsolete outside of fossilized phrases.
Like many other languages, many phenomena in the historical evolution of Hindustani are better explained by the wave model than by the tree model. In particular, the oldest changes like the retroflexion of dental stops and loss of ṛ have been subject to a great deal of dialectal variance and borrowing. In the face of doublets like Hindustani baṛhnā "to increase" and badhnā "to increase" where one has undergone retroflexion and the other has not, it is difficult to know exactly under what conditions the sound change operated. One often encounters sound changes described as "spontaneous" or "sporadic" in the literature (such as "spontaneous nasalization"). This means that the sound change's context and/or isogloss (i.e. dialects in which the sound change operated) have been sufficiently obscured by inter-dialect borrowing, semi-learned adaptations to Classical Sanskrit or Prakrits, or analogical leveling.

## From Vedic Sanskrit to Early Middle-Indo-Aryan

This section summarizes the changes occurring between Vedic Sanskrit (ca. 600 BCE) and the first attestations of Early Middle-Indo-Aryan in Pali or Ashokan Prakrit (ca. 280 BCE).

### Conservative features lost in Vedic

Pali, Prakrit, Hindustani, and many other Indo-Aryan languages partially-preserve some conservative features of Proto-Indo-Aryan (PIA) lost in Vedic Sanskrit, though spontaneous changes produce many counter-examples:
* PIA *kṣ, *gẓʰ merge to Vedic kṣ, but remain distinguished later as kh-, jh- initially and -kkh-, -jjh- medially. Compare PIA Hákṣi > Sanskrit akṣi > Prakrit akkhi "eye" (whence Hindustani ā̃kh) with PIA gẓʰáranam > Vedic kṣaraṇam, later Sanskrit jharaṇam > Prakrit jharaṇa "falling" (whence Hindustani jharnā "to cascade").
* The distinction between PIE *r and *l survived in the "l-dialect" of Indo-Aryan, which went on to form the basis of Classical Sanskrit and Central MIA. The Northwestern Vedic dialect, perhaps under areal influence of Iranian, underwent an l > r shift alongside the same shift in Iranian. Thus, Vedic is part of the "r-dialect" of Indo-Aryan, though /l/ continues to exist as a relatively rarer phoneme in Vedic. Due to the prestige of the Vedic dialect, the r-dialect forms were often accepted into the dialect of Classical Sanskrit and later into Central MIA. More rarely, l is encountered in the later language for PIE *r.
* The l-dialect (and cases of /l/ in Vedic) then possibly underwent Fortunatov's law, wherein pre-Sanskrit dentals *t, *tʰ, *d, *dʱ, *s, and *n underwent cerebralization after PIA *l, after which the *l was deleted. — PIA *ȷ́l̥tʰáram > Sanskrit jaṭhára "stomach, womb".
** Proponents of Fortunatov's law will separate this from the Middle Indo-Aryan rule in which a dental is cerebralized by a preceding rhotic. That later rule only affects plosives (and even then, it operates sporadically), while Fortunatov's law reliably operated in Old Indo-Aryan. It shifts s > ṣ (Proto-Indo-Iranian bʰā̆ls- > Sanskrit bhāṣ- "to speak"), while the distinction between s ~ ṣ ~ ś had already been lost by Middle Indo-Aryan.
* In Vedic and Pali dialects, PIA *ẓḍ > ḷ (ळ) /ɭ/ and*ẓḍʰ > ḷh (ळ्ह) /ɭʱ/. Elsewhere (and regularly in Classical Sanskrit), PIA *ẓḍ > ḍ (ड) /ɖ/ and*ẓḍʰ > ḍh (ढ) /ɖʱ/.

### Early changes common to Dardic

The following changes are common to Middle Indo-Aryan (MIA) and Dardic:
* The unpredictable pitch accent of Vedic was lost, resulting in the mora-timed isochrony of Pali. The pitch accent is sometimes used to explain some irregular consonant doubling (Vedic jitáḥ > Prakrit jitto "won") or differences between Marathi and neighboring languages, indicating that the Vedic accent may have converted to a stress accent (as with Ancient Greek) and persisted in the Maharashtri region. However, this topic is debated and in the case of the irregular consonant doubling there may be alternative explanations.
* Before a consonant, Vedic ए e /ɐj/ and ओ o /ɐw/ monophthongize to /eː/ and /oː/, respectively. In the same position, Vedic ऐ ai /ɑːj/ > /ɑj/ and औ au /ɑːw/ > /ɑw/. This pronunciation is already used in Classical Sanskrit, distinguishing it from Vedic.
* Loss of word-final consonants in a few ways:
** Sanskrit word-final plosives (only /k ʈ t̪ p/) are lost with compensatory lengthening of the preceding vowel.
** Based on the initial consonant of the following word, Vedic word-final visarga /h/ has the allophones [∅], [ɸ], [ɾ], [x], [s], [ɕ], [ʂ], or [w]. Already in Classical Sanskrit, [ɸ] and [x] are not found. Later, Vedic -अः /ɐh/ becomes MIA -ओ /oː/ everywhere. Remaining word-final /h/ was entirely lost without a trace.
** Final nasals are lost with compensatory nasalization of the preceding vowel, indicated by the anusvara. Mishra and Bloch argue that word-final anusvara was realized as nasalization, but elsewhere anusvara was still pronounced as a nasal consonant.
* MIA monophthongization of /ɑj ɐjɐ ɐji ɐjoː ɐvi/ > /eː/. Similarly, /ɑw ɐʋɐ/ > /oː/, though occasionally /ɐʋɐ/ fails to reduce. — Sanskrit avarodhanam /ɐʋɐɾoːd̪ʱɐn̪ɐm/ > Ashokan olodhanaṃ /oːloːd̪ʱɐn̪ɐ̃/ "harem"
* A dental spontaneously cerebralizes to a retroflex stop in the environment of a rhotic. This rule origined in the east, and later to the north and northwest; it was less common in the west. Some scholars like Wackernagel argue that the original cases (or borrowings from eastern dialects) with a retroflex stop in the environment of a rhotic, like prati- > paṭi- and mēḍhra "ram, penis" (already retroflex in Proto-Indo-Aryan *Hmáyẓḍʰram) influence later analogical formation. Due to later dialectal mixture and adaptation to Sanskrit, this sound change ends up occurring fairly sporadically in MIA. For example, as early as Pali we see Sanskrit ardhaḥ /ɐɾd̪ʱɐh/ > Pali addho /ɐd̪ːʱoː/ or aḍḍho /ɐɖːʱoː/ "half". Generally, cerebralization did not happen across a perceived morpheme boundary. Hence, Sanskrit nirdhanaḥ /n̪iɾd̪ʱɐn̪ɐh/ (morphologically nir- "without, -less" + dhana- "wealth") > Prakrit ṇiddhaṇo /nid̪ːʱɐnoː/ "not wealthy". Many cerebralized words were old enough to be borrowed back into Classical Sanskrit, like paṭh- "to read" (from older pṛth- "to spread") with a specialized meaning. See also Fortunatov's Law, a similar rule mentioned above.
* Loss of ṛ is common to Dardic, Pali, and Prakrit (whence Hindustani). The exact sound change depends on the context and region/dialect. In the Central dialect, initial ṛ- > ri and medial -ṛ > i (but cases of ṛ > a and ṛ > u—especially after labial—are occasionally found). Elsewhere (especially in Pali, Western, and Southern dialects), ṛ > a is more common. — Sanskrit ṛṇa > Prakrit riṇa "debt" (whence Hindustani rin) and Sanskrit kṛta > Prakrit kida, kia "done" (whence Hindustani kiyā).

### Common sound changes between Pali and Prakrit

After the split of Dardic languages, the these changes are common to Pali and Prakrit. These changes may be also grouped together as the "MIA assimilation rules", and are the most important rules from this period. Regarding the assimilations of Old Indo-Aryan consonant conjuncts, the Jayadhavalā (ca. ninth century AD) writes Dīsaṁti doṇṇi vaṇṇā saṁjuttā aha va tiṇṇi cattāri / Tāṇaṁ duvvala-lōvaṁ kāūṇa kamō pajuttavvō "When two, or three or four, consonants appear in combination, elide the weakest one, and continue the process." Here, "weakest" refers to sounds of higher sonority, and "elide" refers to either true elision/loss or total assimilation of the weaker sound to the stronger sound. Specifically, the sonority scale of Prakrit is (weakest) h < r < y < v < l < nasals (m, n, ṇ, ñ) < s (representing OIA sibilant series) < all stops (strongest). It will be helpful to keep this notion of "stronger" and "weaker" sounds in mind through the following sound changes. The relevant changes (organized by approximate chronology) are.
* The sibilant series (ś /ɕ/, ṣ /ʂ/, and s /s/) merges in most regions to s /s/. In the Eastern region (e.g. Magadhan), it merges instead to ś /ɕ/. In Romani, the original three-way sibilant distinction is preserved. — Sanskrit daśa /d̪ɐɕɐ/ > Prakrit dasa /d̪ɐsɐ/ (whence Hindustani das "ten").
* After a non-nasal dental or retroflex stop, /m/ and /ʋ/ assimilate to /p/ if the stop is unvoiced or /b/ is the stop is voiced. This stage is attested at Girnar — Sanskrit catvāraḥ /t͡ʃɐt̪ʋɑːɾɐh/ > Girnar Ashokan catpāro /t͡ʃɐt̪pɑːɾoː/
* Vedic jñ /dʑɲ/, ny /n̪j/, and ṇy /ɳj/ > MIA ññ /ɲː/. Occasionally, jñ /dʑɲ/ > jj /d̪d͡ʒ/.
* Epenthetic /b/ arises in -mr- /mɾ/ > -mbr- /mbɾ/ and -ml- /ml/ > -mbl- /mbl/. — Sanskrit āmraḥ /ɑːmɾɐh/ > */ɑːmbɾɐh/ > Prakrit aṃbo /ɐmboː/ "mango", whence Hindustani ām "mango"
* A succeeding /j/ palatalizes a dental stop and a succeeding sibilant palatalizes /t̪/ and /p/. This tendency is represented scarcely in some "corruptions" in Sanskrit, like jyotiḥ /d͡ʒjoːt̪ih/ "light" < PIA *dyáwtiṣ.
* When a long vowel precedes a consonant cluster, the long vowel is shortened. More rarely, a long vowel was retained at the expense of simplifying the consonant cluster. This tendency is seen in the older language; for example, Classical Sanskrit kalyam /kɐljɐm/ "dawn" (< Vedic kālyam /kɑːljɐm/) or margaḥ /mɐɾɡɐh/ "path" (< Vedic mārgaḥ /mɑːɾɡɐh/). In the case of e (ए) /eː/ and o (ओ) /oː/, this produces the short allophones /e/ and /o/. These allophones are generally not distinguished orthographically, but a distinction is made in romanization as ĕ and ŏ (with breve marks).
* A consonant cluster of three or more consonants is reduced to two consonants by elision from either the left or right, with some variation. — Vedic tīkṣṇáh /t̪iːkʂɳɐ́h/ > either Prakrit tikkho /t̪ikːʰoː/ or tiṇho /t̪inɦoː/ "sharp". In the first, /ɳ/ was deleted from the right and by a later sound change /kʂ/ > /kːʰ/. In the second, /k/ was deleted from the left and by a later sound change /ʂɳ/ > /ɳɦ/. In either case, the /iː/ shortens as it occurs before a consonant cluster. Prakrit tikkho /t̪ikːʰoː/ later becomes Hindi tīkhā /t̪iːkʰɑː/ "spicy, sharp".
* kṣ /kʂ/ > kh- /kʰ/ initially or -kkh- /kːʰ/ elsewhere. In the Central and Eastern regions, this outcome would naturally occur from the sound changes below. It is worth mentioning because in other regions, the special sequence kṣ /kʂ/ > ch- /t͡ʃʰ/ initially and -cch- /t͡ːʃʰ/ elsewhere. There is some dialectal borrowing already seen in Pali (which usually attests the -(k)kh- variant but sometimes has -(c)ch-) and regional Ashokan Prakrit.
* In a cluster with a plosive or affricate (always) or when followed by a nasal consonant (usually, but not always), s /s/ weakens to h /ɦ/. Alternatively when followed by a nasal consonant, the s can be retained (especially medially, where by the cluster simplification rule below the cluster becomes -ss-) or anaptyxis can break the cluster.
* When h /ɦ/ (either from older sibilant via the above rule or otherwise) precedes a consonant, the consonant and /ɦ/ metathesize. — Sanskrit cihnam /t͡ʃiɦn̪ɐm/ > Pali cinhaṃ /t͡ʃin̪ɦɐ̃/ "sign".
* At the start of a word, the sequence of an obstruent (i.e. non-sonorant) + h /ɦ/ simply results in an aspirated plosive or affricate. Elsewhere, the h /ɦ/ undergoes regressive assimilation by transforming into the aspirated equivalent of the plosive or affricate. The last rule is already known in Sanskrit sandhi, where, for example, tad + hi → taddhi, rather than *tadhi so as to preserve the syllable weight of the first syllable. — Sanskrit vatsaḥ ~ vatso /ʋɐt̪soː/ > */ʋɐt͡ʃsoː/ (palatalization) > */ʋɐt͡ʃɦoː/ (sibilant weakening) > /ʋɐt͡ːʃoː/ (sandhi of -c- + -h- → -cch-) > Pali vaccho /ʋɐt͡ːʃoː/ "calf".
* Cluster simplification: The main rule being referred to in the above Jayadhavalā quote. All consonant clusters are simplified to achieve the MIA phonotactic situation where syllables are restricted to at most a CVC structure (where the coda C is further restricted to either the anusvara ṃ, a nasal/plosive homorganic to the following syllable onset C, or a sonorant if the following syllable onset is h /ɦ/). Word-initially, only the strongest sound in a cluster survives — Sanskrit grāmaḥ /gɾɑːmɐh/ > Ashokan gāmo /gɑːmoː/ "village". Medially, the weaker sound totally assimilates to the stronger sound, and sequences like -CʰC- or -CʰCʰ- are immediately repaired to -CCʰ- — Sanskrit vyāghraḥ /ʋjɑːgʰɾɐh/ > */ʋjɐgʰɾoː/ (prior sound changes) > /ʋɐgːʰoː/ (initial /ʋj/ > /ʋ/, medial /gʰɾ/ > /gːʰ/, not */gʰg/) > Pali and Prakrit vaggho /ʋɐgːʰoː/ "tiger".
* The treatment of a sonorant + h /ɦ/ is complicated. Generally, aspirated sonorants are not phonemic in Pali or Prakrit, meaning yh /jɦ/, rh /ɾɦ/, lh /lɦ/, vh /ʋɦ/, ñh /ɲɦ/, ṇh /ɳɦ/, nh /n̪ɦ/, and mh /mɦ/ are all treated as a sequence/cluster of two consonants. However, these sequences are treated specially among the variety of consonant clusters, particularly because they are permitted word-medially. Word-initially, the result is varied. In Pali, epenthetic -a- breaks the sequence — Sanskrit hradaḥ /ɦɾɐd̪ɐh/ > */ɾɦɐd̪oː/ (prior sound changes) > Pali rahado /ɾɐɦɐd̪oː/ "lake". In Prakrit, this sequence is either permitted (especially in Maharashtri Prakrit), epenthetic -a- appears to break the sequence, or the h /ɦ/ is dropped. — Sanskrit snānam /sn̪ɑːn̪ɐm/ > Prakrit ṇhāṇa /n(ɐ)ɦɑːnɐ/ "bathing", whence Hindustani nahānā "to bathe" (but also Prakrit siṇāṇa /sinɑːnɐ/ and saṇāṇa /sɐnɑːnɐ/, where the s > h rule did not occur and early anaptyxis breaks the cluster) and Sanskrit snasā /sn̪ɐsɑː/ > Prakrit ṇasā /nɐsɑː/ "tendon, sinew", whence Hindustani nas "tendon, sinew".
* The sequence -sr- /sɾ/ can sometimes yield -ṃs- /ns/ rather than expected -ss- /sː/. — Sanskrit aśru /ɐɕɾu/ > Prakrit assu /ɐsːu/, aṃsu /ɐnsu/, whence Hindustani ā̃sū "tear".
* The sequence -mh- /mɦ/ can sometimes fortify to -ṃbh- /mbʱ/.
* In general, anaptyxis, rather than assimilation, can be applied to break a heterogeneous cluster. This is most common in cases of a stop followed by sonorant, as in -tn-, -dm-, -kl-, etc. — Sanskrit ratna > Pali ratana or Sanskrit klēśa > Prakrit kilēsa > Hindustani kales "grief".

### Changes after the split of Pali and Prakrit

The following changes are only seen in Prakrit and not in Pali (other Pali-specific changes do also occur beyond this point):
* yh /jɦ/ and vh /ʋɦ/ become jh- /d͡ʒʱ/ and bh- /bʱ/ initially and -jjh- /d͡ːʒʱ/ and -bbh- /bːʱ/ medially. In Pali, only /ʋɦ/ changes. — Sanskrit guhyaḥ /guɦjɐh/ > /gujɦoː/ (prior sound changes) > Pali guyho /gujɦoː/, but develops further into Prakrit gujjho /gud͡ːʒʱoː/.
* Relatedly, initial y /j/ fortifies to j /d͡ʒ/ and medial yy /jː/ > jj /d͡ːʒ/.— Sanskrit yaḥ /jɐh/ > Pali yo /joː/, Prakrit jo /d͡ʒoː/, whence Hindustani jo "that, what".
* In Pali, geminate -vv- /ʋː/ > -bb- /bː/, but this never occurred in Prakrit generally. However, in the Central and Eastern region, initial /ʋ/ > /b/ and medial geminate /ʋː/ > /bː/ has occurred before New Indo-Aryan. It can be argued that this fortification occurs earlier alongside the fortification of /j/ > /d͡ʒ/, and orthographic व् /ʋ/ beyond this point is merely conservative.
* Cases of -ēy- /eːj ~ ejː/ and -ī̆y- /iːj ~ ijː/ are re-analyzed as having a geminate glide and undergo the above rule as well. — Sanskrit kālēyam /kɑːleːjɐm/ > Prakrit kālēyaṃ /kɑːleːɐ̃/, kālijjaṃ ~ *kālĕjjaṃ /kɑːlid͡ːʒɐ̃ ~ kɑːled͡ːʒɐ̃/, whence Hindustani kalejā "liver".
* In Pali, Sanskrit jñ /dʑɲ/ becomes ñ- /ɲ/ initially and -ññ- /ɲː/ medially. In Prakrit, the result is usually j- /d͡ʒ/ initially and -jj- /d͡ːʒ/ medially. Sometimes, ñ- /ɲ/ initially and -ññ- /ɲː/ medially are found too.
* As noted before, the reflex of Sanskrit ṛ is different in Pali, Prakrit, and Dardic (e.g. initial ṛ > Prakrit ri- always, but Pali and Dardic a-, i-, u-). Also, the reflex of Sanskrit clusters involving a sibilant and sonorant is unstable between Pali and Prakrit.

### Orthographic changes

* Before a consonant, ṅ, ñ, ṇ, n, m, and the anusvara ṃ are in complementary distribution. In Sanskrit, each different nasal consonant is typically written out. In later languages, all pre-consonant nasals are written as the anusvara ṃ.
* The Sanskrit long vowels ē and ō are sometimes romanized as e and o (without the macron) since Sanskrit didn't have short versions of these vowels so there is no ambiguity. The romanization of long ē, ō and short ĕ, ŏ in Prakrit has been discussed

## Up to Dramatic Prakrits

These changes occur after Pali and Early Prakrit, but before the development of the dramatic regional Prakrits like Maharashtri Prakrit and Shauraseni Prakrit (ca. 200 AD):
* Merging of nasals ṇ, n > ṇ (n̪ ɳ > n), represented as a retroflex nasal. Whether the actual place of articulation of this sound was truly retroflex or was dental (and just orthographically represented as a retroflex nasal) is debated. Regardless, this sound regularly becomes Hindustani dental n later on (but intervocalically, the sound becomes ṇ in other languages like Marathi, Gujarati, and Punjabi).
* Lenition of intervocalic stops over time, through various attested stages. First, all single intervocalic unvoiced stops become voiced. Then, non-retroflex stops spirantize (one possibility is g, gʱ, dʒ, d, dʱ, b, bʱ > ɣ, ɣʱ, ʑ, ð, ðʱ, β, βʱ / V_V). Per Chatterji, this stage is represented by vacillation between writing a voiced stop, semivowel, or nothing. The retroflex voiced stops ḍ, ḍh likely become flaps intervocalically (the reflex ultimately in Hindustani), but this distinction is not represented orthographically. Finally, aspirated spirants debuccalize (ɣʱ, ðʱ, βʱ > ɦ), the spirant β > ʋ (romanized as v), and remaining spirants ɣ, ʑ, ð are lost, leaving the surrounding two vowels in hiatus. — Sanskrit kathanam /kɐt̪ʰɐn̪ɐm/ > Prakrit kahaṇaṃ /kɐɦɐnɐ̃/ "saying", whence Hindustani kahnā "to say".
* Between two ā̆ vowels, hiatus is usually resolved by what Hemachandra, in his grammar of Prakrit, calls a “lightly pronounced y-sound” (laghuprayatnatarayakāraśrutiḥ). As far as orthography/romanization is concerned, this results in the optional inclusion of epenthetic -y- or less likely -v- between the ā̆ vowels. This orthographic choice should not be confused with the older genuine /j/ phoneme. Similarly, after a front vowel, euphonic/orthographic -y- appears. Elsewhere, hiatus is fully tolerated. After ā̆, the diaeresis is often used in romanization (e.g. aï, aü) to differentiate this sound from the older overlong vowels.
** Sanskrit śoka- /ɕoːkɐ/ > Pali/Ashokan soka- /soːkɐ/ > Early Dramatic Prakrit soga- /soːgɐ ~ soːɣɐ/ > Prakrit sōa- /soːɐ/ "sorrow"
** Sanskrit caturtha- /tɕɐt̪uɾt̪ʰɐ/ > Pali/Ashokan catuttha /t͡ʃɐt̪ut̪ːʰɐ/ > Early or Shauraseni Dramatic Prakrit caduttha- /t͡ʃɐd̪ut̪ːʰɐ ~ t͡ʃɐðut̪ːʰɐ/ > Prakrit caüttha- /t͡ʃɐut̪ːʰɐ/, whence Hindustani cauthā "fourth".
* Occasionally, intervocalic -d- /d̪/ became -r- /ɾ/, as in the numbers from 11 to 18.
* Lenition of intervocalic y /j/, similarly to the above change. The optional inclusion of epenthetic -y- sometimes makes this confusing, but at this point /j/ is no longer phonemic in Prakrit; it is merely an epenthetic hiatus-filler. — Sanskrit nayanam /n̪ɐjɐn̪ɐm/ > Prakrit ṇa(y)aṇaṃ /nɐɐnɐ̃/, whence Hindustani nainā "eyes".
* Lenition of intervocalic v /ʋ/ between ā̆ and a high vowel. — Sanskrit praviṣṭa- /pɾɐʋiʂʈɐ/ > Prakrit païṭṭha- /pɐiʈːʰɐ/ > Hindustani paiṭhā "entered", but Sanskrit nava /n̪ɐʋɐ/ > Prakrit ṇava /nɐʋɐ/ > Hindustani nau "nine" with retention of -v-.
* Occasionally, the sequences aï and aü contracted early on in Prakrit to ē̆ and ō̆. This a separate change than the later coalescence of vowels in hiatus. — Sanskrit sthavira- /st̪ʰɐʋiɾɐ/ > Earlier Prakrit ṭhavira- /ʈʰɐʋiɾɐ/ > *ṭhaïra- /ʈʰɐiɾɐ/ > Later Prakrit ṭhēra- /ʈʰeːɾɐ/ "old".
* Prakrit ḍ, ḷ, l, and r often alternate with each other, particularly in words loaned from non Indo-Aryan sources.
** PIA *swaẓḍaśa > Sanskrit ṣoḍaśa > Prakrit solasa /soːlɐsɐ/ > /soːlɐɦɐ/, whence Hindustani solah "sixteen"

### Pleonastic Suffixes

Another change worth noting here that will become more prevalent by late MIA and early NIA is the extension of Old Indo-Aryan nominals and roots with pleonastic suffixes. The consensus, implied by the name, is that these innovative suffixes have little semantic purpose and mainly serve to distinguish homophones (created by the sweeping sound changes between Sanskrit and Prakrit). They are applied after nominal and verb stems, before inflecting suffixes. Some are recognizable as the reflexes of Old Indo-Aryan diminutive suffixes.
The most important suffixes are feminine -iā- (< earlier -igā < Sanskrit -ikā) and masculine -a- (< earlier -ga < Sanskrit -ka). The equivalent Sanskrit endings were already common in Old Indo-Aryan as diminutives, but become more popular at this stage and ultimately become the "marked" declension of nouns in Hindustani and other Indo-Aryan languages.
* (Sanskrit karpaṭa >) Prakrit kappaḍa + -a- > *kappaḍa(y)a > Hindustani kapṛā "clothing"
* (Sanskrit kaṭa "twist of straw" >) Prakrit kaḍa + -iā- > *kaḍiā > Hindustani kaṛī "chain link"
* (Sanskrit naptṛ "grandson" >) Prakrit natti + -a- > nattia > Hindustani nātī "grandson"
The other common suffixes are -kka-, -ḍa-, -illa-, -la-, -lla-, -ulla-, and -ra-. These suffixes are very often combined with each other:
* (Sanskrit markaṭa >) Prakrit makkaḍa + -ḍa- + -iā > *makkaḍiā > Hindustani makṛī "spider"
* (Sanskrit matsya >) Prakrit maccha + -lla- + -iā > *macchaliā > Hindustani machlī "fish" (but also unextended Prakrit maccha > Hindustani māch)

## Up to Apabhramsha

These changes occur after the dramatic Prakrits, and characterize the Late Prakrit, or Apabhramsha, stage (ca. 900 AD).
* Intervocalic -m- becomes a nasalized glide /ʋ̃/, and then the nasalization is shifted on the preceding or following vowel. This change notably did not occur in the Western zone (e.g. Gujarati).
** (Sanskrit grāma >) Pali/Prakrit gāmo /gɑːmoː/ > Central Apa. /ˈgɑː.ʋ̃u/ > Hindustani gā̃v /ɡɑ̃ːʋ/ "village", but Gujarati gām
* Prakrit final long vowels shorten and change in quality if necessary to merge with the short vowels: /ɑː iː uː eː oː/ > /ɐ i u i u/. This tendency is known since at least Ashokan times, where originally-long final vowels are frequently shortened and short vowels are confused with the long form (in a manner of orthographic conservatism)—we find Ashokan tada /t̪ɐd̪ɐ/ for Sanskrit tadā /t̪ɐd̪ɑː/ "then", Ashokan Ambika /ɐmbikɐ/ for Sanskrit Ambikā /ɐmbikɑː/, etc.
* Intervocalic -v- /ʋ/ is lost after a high vowel.
* Long ū is shortened before another vowel — (Sanskrit kūpa- /kuːpɐ/ >) Prakrit kūva- /kuːʋɐ/ > Apa. /ˈku.ɐ.u/, whence Hindustani kuā "well"
* Development of a Latin-like positional stress system. Stress falls on the penultimate syllable if it is heavy, failing which it falls on the antepenultimate syllable if it is heavy, failing which it falls on the fourth syllable from the end. This system retroactively came to characterize Classical Sanskrit, but it can be considered a MIA development that was only fully completed around the Apabhramsha stage.

## Up to Hindustani

Changes after this point characterize the New Indo-Aryan (NIA) era from the MIA period. These changes start to distinguish Hindi from nearby languages like Marathi, Gujarati, and Punjabi. Many of these rules are sporadically underway already in Late Prakrit/Apabhramsha.

### Up to Old Hindi

The following changes, organized approximately chronologically, characterize some varieties of Old Hindi:
* Retroflex ṇ, ḷ are dentalized to n, l.
* Intervocalic -v- is lost around -ī̆-. This explains why we have Hindustani tavā "tawa" (< Prakrit tavaa) but taī "griddle" (< Prakrit taviā), both from the same root. Compare Marathi, Punjabi, and Gujarati tavī "griddle". In some cases, like Hindustani dī̆yā < Prakrit dīvau, the variant in -v- (dīvā) is found in Modern Hindustani as a regional variant. In Hindustani, this process went much further than in other regions, and analogical leveling sometimes caused the -v- to be lost altogether. — Prakrit ṇavaa, ṇaviā > Old Hindi navā ~ naī or nayā ~ naī > Hindustani nayā ~ naī "new" (with dialectal/archaic navā). For this, we have Marathi, Gujarati, and Punjabi navā ~ navī.
* Initial v- > b- and medial geminate -vv- > -bb- — Prakrit vāla > Old Hindi bāla "hair", but Gujarati vāḷ.
* ī is shortened before a vowel. — Prakrit dīva- /d̪iːʋɐ/ > /d̪iːɐ/ > /d̪iɐ/ > Hindustani diyā "lamp".
The following changes can be grouped as "vowel coalescence" rules and will reduce the frequency of vowels in hiatus. They are present to some degree in most NIA languages:
* The sequences aü /ɐ.u/ and aï /ɐ.i/ become diphthongs ai /a͡ɪ/ and au /a͡ʊ/. —Prakrit païjjā /pɐid͡ːʒɑː/ > Old Hindi paija /ˈpa͡ɪ.d͡ʒɐ/ "vow", whence Hindustani paij.
* The sequence of ā /ɑː/ + short /i/ or /u/ gives rise to new overlong diphthongs āv /ɑːʋ/ and āy /ɑːj/.
* Short or long vowels in hiatus of like quality (except short a /ɐ/ + a /ɐ/ which will be discussed later) coalesce to a long vowel. — Prakrit duuṇa- /d̪uunɐ/ > Old Hindi dūna /ˈd̪uː.n̪ɐ/ "twice", whence Hindustani dūnā.
* When followed by a stressed vowel, short /i/ or /u/ become glides. — Prakrit pivāsā /piʋɑːsɑː/ > Apa. /piˈɑː.sɐ/ > Old Hindi pyāsa /ˈpjɑː.sɐ/ "thirst", whence Hindustani pyās.
* When a short, unstressed vowel is preceded by /i(ː) u(ː) eː oː/, the second vowel is lost and the first vowel is lengthened if short. — Prakrit sīala- /siːɐlɐ/ > Apa. /ˈsiː.ɐ.lɐ/ > Old Hindi sīla /ˈsiː.lɐ/ "cold", whence Hindustani sīl.
* The Prakrit sequence of short a /ɐ/ + a /ɐ/ generally coalesces the diphthong ai /a͡ɪ/, but can sometimes contract further to e /eː/. — Prakrit ṇaaṇa- /nɐɐnɐ/ > Old Hindi naina /ˈn̪a͡ɪ.n̪ɐ/ "eyes", whence Hindustani nain.
* Similarly, the Prakrit sequence ava /ɐʋɐ/ can contract to the diphthong au /a͡ʊ/, but can sometimes contract further to o /oː/.
** Turner explains the occasional further contraction of ai > e and au > o (at least for Gujarati) in terms of inherited words versus semi-learned words: in the former the process has had time to go further. A similar explanation of occasions where -y- possessed more reality could be drawn up to word frequency, dialectal borrowing, and semi-learned borrowings.
* In remaining cases or in if a morpheme boundary is felt between the vowels in hiatus, vowels may not coalesce. A semivowel may optionally appear to fill the hiatus.
The remaining sound changes relate to the lengthening and shortening of vowels:
* Simplification of consonant clusters: For stressed syllables, the general rule is VCː > VːC and VNC > ṼːC. That is, a consonant cluster is simplified and the preceding vowel undergoes compensatory lengthening or lengthening + nasalization. Per usual, a /ɐ/ lengthens and shifts in quality to ā /ɑː/. Short allophonic ĕ /e/ and ǒ /o/ always elongate to e /eː/ and o /oː/. This change occurred in all regions in some form, excluding the Northwest (e.g. Punjabi). Generally, this sound change had already occurred in the East by the eighth century AD, based on inscriptions found in East Bengal and Chinese-Sanskrit dictionaries of the time. It was probably completed in the Central region by the tenth century.
** Prakrit satta /sɐt̪ːɐ/ > Old Hindi sāta /ˈsɑː.t̪ɐ/ "seven", whence Hindustani sāt.
** Prakrit saṃjhā /sɐnd͡ʒɑː/ > Old Hindi sā̃jha /ˈsɑ̃ː.d͡ʒɐ/ "evening", whence Hindustani sā̃jh.
* Compensatory lengthening from older geminates was sometimes accompanied by spontaneous (and regionally random) nasalization of the vowel. In some cases, this goes back to Prakrit or is otherwise reflected in nearby NIA languages.
* Unstressed syllables generally underwent VCː > VC and VNC > VNC, i.e. the vowel is left short. — Prakrit kappūra- /kɐpːuːɾɐ/ > Old Hindi kapūra /kɐˈpuː.ɾɐ/ "camphor", whence Hindustani kapūr. Observe that this does not characterize, for example, Old Marathi, where the cognate is kāpūra with lengthening of a > ā.
* When a stressed VCː or VNC syllable is preceded by another heavy syllable (i.e. of the form Vː(C), VCː, or VNC), it will also sometimes undergo VCː > VC and VNC > VNC with no compensatory lengthening, shifting stress onto the preceding syllable. — Prakrit pālakka- /pɑːlɐkːɐ/ > Old Hindi pālaka /ˈpɑː.lɐ.kɐ/ "spinach", whence Hindustani pālak. Occasionally, though, compensatory lengthening will occur, as in Prakrit bhattijja- /bʱɐt̪ːid͡ːʒɐ/ > Old Hindi bhatījā /bʱɐˈt̪iː.d͡ʒɑː/ "nephew", whence Hindustani bhatījā.
* Pre-tonic and word rhythm vowel shortening: Long vowels (often resulting from compensatory lengthening) are generally shortened (accompanied by a change in quality if necessary) before two or more syllables where at least one of the syllables is heavy. That is, ā > a (ɑː > ɐ), e ī > i (eː iː > i), o ū > u (oː u > u). This rule is fairly productive in Modern Hindustani and partially explains Hindi's distinctive ablaut alterations when certain words are suffixed.
** Old Hindi miṭhāī /miˈʈʰɑː.iː/ "dessert, sweetness" (rather than *mīṭhāī) from mīṭhā /ˈmiː.ʈʰɑː/ "sweet".
** Old Hindi chuṛāe /t͡ʃʰuˈɽɑː.eː/ "causes to leave, expels" (rather than *choṛāe) from coṛe /ˈt͡ʃʰoː.ɽeː/ "leaves".
** Old Hindi nicalā /ˈn̪i.t͡ʃɐ.lɑː/ "lower" (rather than *nīcalā) from nīcā /ˈn̪iː.t͡ʃɑː/ "low".
The above rules and their caveats still do not sufficiently explain all cases of vowel length and gemination encountered in Hindustani, but it is closest to the ordering of the rules that Turner proposes in his analyses of Gujarati, Marathi, and Hindi. More complex phenomena must be employed to explain the counter-examples. For the remaining cases:
* The Prakrit participle suffix -aṃta- simply loses nasalization and becomes Old Hindi -atā̆, whence Hindustani -tā, as in kartā "doing".
* Some examples are explained as semi-learned adaptation to Sanskrit. For instance, from Prakrit suddhi /sud̪ːʱi/, one would expect Old Hindi sūdha /ˈsuː.d̪ʱɐ/ but we instead find sudha /ˈsu.d̪ʱɐ/ "memory, sense" (> Hindustani sudh), under influence of the vowel length in the Sanskrit etymon śuddhi.
* In verbs, the length of the vowel is frequently manipulated to reflect the transitivity of the verb. This tendency is known since Sanskrit (compare passive tapyate "is heated" with active tāpayati "heats, causes to heat up"). From Prakrit tappaï /t̪ɐpːɐi/ we get the Hindustani pair tape /t̪ɐ.peː/ "is heated" and tāpe /t̪ɑː.peː/ "heats, causes to heat up".
* In some multi-syllabic words, the VCː or VNC sequence was left unsimplified, perhaps due to borrowing from the northwest (whence Punjabi and Sindhi). The vowel lengthening rules did not take place in the northwestern region (words with this sound change in Punjabi and Sindhi are themselves borrowings from other Indo-Aryan languages, like Hindustani). These borrowings, likely from a Western Hindi dialect transitional to Punjabi, result in a large number of doublets in Hindustani. From Prakrit makkhaṇa- /mɐkːʰɐnɐ/, we get the Hindustani pair mākhan /mɑː.kʰən̪/ and makkhan /mək.kʰən/, both meaning "butter".
* Other cases of vowel reduction in common, unstressed grammatical words.

### Sound changes from Old Hindi through modern Hindustani

* Final nominative -au > -ā. -au is retained in the second-person plural suffix (from where it later becomes Hindustani -o).
* Attenuation of post-tonic and final short vowels to /ǝ/. A number of words are saved from this lenition by semi-learned lengthening of the final vowel. For instance, from Sanskrit guru > Prakrit guru > Old Hindi gura, but also the semi-learned variant gurū "teacher, guide"
* Suffix weakening: During the Old Hindi stage, final unstressed -ai and -au monophthongized to -e and -o, respectively. Hence, the general third-person singular ending underwent Sanskrit -ati > Prakrit -adi > Apabhraṃśa -aï > Old Hindi -ai > Hindustani -e, but when it was stressed in the monosyllabic Old Hindi hai, it remains unsimplified in Hindustani hai "is".
* Indo-Aryan schwa deletion: ə → ∅ / VC_CV, though the application of this rule (particularly when there are many schwas in sequence) is dependent on the morphological boundaries of the word. This change is not indicated in the Devanagari script for Hindustani. — Old Hindi rāta > Hindustani rāt "night"
** This resulting in some ablaut alterations throughout a single verbal paradigm. For example, the infinitive utarnā "to descend" has the past participle utrā "descended", where the intertonic vowel in Old Hindi utarā has been lost.
* -nr- > -ndr- by epenthesis, where cases of -nr- arise from schwa deletion. — Prakrit paṇṇaraha > Old Hindi panaraha > *panrah (schwa deletion) > Hindustani pandrah, pandrā "fifteen"
* Unstressed (short) vowels are also lost in other positions, particularly initial vowels in words of 3 or more syllables or intertonic short vowels. — Old Hindi aḍhā́ī > Hindustani ḍhāī "two and a half"
* Lenition of Ṽbh > Vmh and Ṽb > Vm: This change was a dialectal feature, and in regional Hindi variants the archaic form persists. In some cases, the regional variant which did not undergo this change ended up supplanting the main-dialect form, at least in writing.
** Old Hindi tā̃ba > Hindustani tām "copper (in compounds)", with regional variant tā̃b
** Old Hindi kũbhāra > Hindustani kumhār "potter", with regional variant kũbhār
** Old Hindi ā̃ba > Hindustani ām "mango", with regional variant ā̃b (compare Marathi āmbā, where this sound change never occurred)
** Old Hindi sãbhālanā > Hindustani sãbhālnā, with the pronunciation-spelling variant samhālnā
** The common root samajh- "to understand" from Prakrit saṃbujjh- should be treated as an irregular case because the ṃbh > mh > m shift and shifting of stress to the first syllable (hence confusion of post-tonic u > a) occurred in Pre-New-Indo-Aryan, hence it is present in Old Hindi and languages like Marathi which usually don't have this lenition rule.
* Loss of nasal aspiration if not pre-vowel: This rule is fed by schwa-deletion and lenitions of Ṽb(h). It explains why Hindustani has mh in tumhārā "your" but no h in tum "you" (< *tumh < older tumha).
* Sounds from loanwords: The sounds /f, z, ʒ, q, x, ɣ/ are loaned into Hindi-Urdu from Persian, English, and Portuguese.
** In Hindi, /f/ and /z/ are most well-established, but can be /pʰ/ or /bʰ/ in rustic speech. /q, x, ɣ/ are variably (by dialect) assimilated into /k, kʰ, g/, respectively, and /ʒ/ is almost never pronounced and substituted by /ʃ/ or /dʒʰ/.
** /pʰ/ is starting to merge into /f/ in a number of Hindustani dialects.
** Sanskrit ṛ is borrowed into Hindustani as /rɪ/, but is pronounced more like /ru/ in languages like Marathi.
* Monophthongization of ai to /ɛː ~ æː/ and au to /ɔː/ in many non-Eastern dialects. A separate /æː/ arguably exists in Hindustani by English loanwords.
* Shifts before /ɦ/: Before h + a short vowel or deleted schwa, the pronunciation of short a shifts allophonically to short [ɛ] or [ɔ] (only if the short vowel is u). This change is part of the prestige dialect of Delhi, but may not occur to the full degree for every speaker. Often, this step is taken further by assimilation of short vowel after /ɦ/ to [ɛ] or [ɔ], and then by loss of /ɦ/ and coalescence/lengthening of vowels into long /ɛː/ and /ɔː/. In some cases, different inflections of the same word have differing outcomes
** Hindustani bahut /bǝ.ɦʊt̪/ > [bɔ.ɦʊt̪] > [bɔ.ɦɔt̪] > [bɔːt̪] "a lot, many"
** Hindustani pahlā /pǝɦ.läː/ > [pɛɦ.läː] > [pɛː.läː] "first"
** Hindustani bahan /bǝ.ɦǝn/ > [bɛ.ɦǝn] > [bɛ.ɦɛn] > [bɛːn] "sister"
** Hindustani kahnā /kǝɦ.näː/ > [kɛɦ.näː] > [kɛː.näː] "to say", but kahegā "he will say" is still pronounced [kǝ.ɦeː.gäː]

## Examples of sound changes

The following table shows a possible sequence of changes for some basic vocabulary items, leading from Sanskrit to Modern Hindustani. All entries are romanized. An empty cell means no change at the given stage for the given item. Only sound changes that had an effect on one or more of the vocabulary items are shown. Words may not be attested at each stage.
| Gloss | juhi | tiger | donkey | dusky | it grows | two and half | to support |
| Sanskrit (nominative) | yūthikā | vyāghraḥ | gardabhakaḥ | śyāmalakaḥ | utpadyati | ardhatṛtīyaḥ | sambhālanam |
| Sandhi (e.g. final -aḥ > -ō) | | vyāghrō | gardabhakō | śyāmalakō | | ardhatṛtīyō | saṃbhālanaṃ |
| Early Cerebralization | | | | | | arḍhatṛtīyō | |
| Loss of ṛ | | | | | | arḍhatatīyō | |
| Sibilant merger | | | | syāmalakō | | | |
| C + y, s palatalization | | | | | utpajyati | | |
| Initial cluster simplif. | | vāghrō | | sāmalakō | | | |
| Two-mora rule | | vaghrō | | | | | |
| Medial cluster simplif. | | vagghō | gaddabhakō | | uppajjati | aḍḍhatatīyō | |
| Pali | yūthikā | vagghō | gaddabhakō | sāmalakō | uppajjati | aḍḍhatatīyō | saṃbhālanaṃ |
| Init. y > j, med. yy > jj | jūthikā | | | | | | |
| Merging of nasals | | | | | | | saṃbhālaṇaṃ |
| Intervocalic lenitions | jūhiā | | gaddahaō | sāmalaō | uppajjaï | aḍḍhaaīō | |
| Pleonastic suffix additions | | | | | | | saṃbhālaṇaō |
| Prakrit | jūhiā | vagghō | gaddahaō | sāmalaō | uppajjaï | aḍḍhaaīō | saṃbhālaṇaō |
| -VmV- > -VṃvV- | | | | saṃvalaō | | | |
| Shorten final long vowels | jūhia | vagghu | gaddahaü | saṃvalaü | | aḍḍhaaīu | saṃbhālaṇaü |
| Positional stress | jū́hia | vágghu | gáddahaü | sáṃvalaü | uppájjaï | aḍḍháaīu | saṃbhā́laṇaü |
| Dentalization of ṇ, ḷ | | | | | | | saṃbhā́lanaü |
| vv > bb and initial v > b | | bágghu | | | | | |
| Vowels in hiatus coalesce | jū́hī | | gáddahau | sáṃvalau | | aḍḍhā́ī | saṃbhā́lanau |
| VCː > VːC or VṃC > ṼːC | | bā́ghu | gā́dahau | sā̃valau | ūpā́jaï | āḍhā́ī | sā̃bhā́lanau |
| Pre/post-tonic vowel shortens | | | | | upā́jaï | aḍhā́ī | sãbhā́lanau |
| Word rhythm shortening | | | gádahau | | upájaï | | |
| Final nominative -au > -ā | | | gádahā | sā̃valā | | | sãbhā́lanā |
| Final short vowels > /ǝ/ | | bā́gha | | | | | |
| Old Hindi | jūhī | bāgha | gadahā | sā̃valā | upajai | aḍhāī | sãbhālanā |
| Final -ai, -au > -e, -o | | | | | upaje | | |
| Schwa deletion | | bāgh | gadhā | sā̃vlā | upje | | sãbhālnā |
| Unstressed initial vowel loss | | | | | | ḍhāī | |
| -Ṽbh-, -Ṽb- > -Vmh-, -Vm- | | | | | | | samhālnā |
| Hindustani Romanized | jūhī | bāgh | gadhā | sā̃vlā | upje | ḍhāī | samhālnā |
| Hindustani Devangari | जूही | बाघ | गधा | साँवला | उपजे | ढाई | सम्हालना |
| Hindustani Urdu | جوہی | باگھ | گدھا | سانولا | اپجے | ڈھائی | سمہالنا |