Hindustani, the lingua franca of Northern India and Pakistan, has two standardised registers: Hindi and Urdu. Grammatical differences between the two standards are minor but each uses its own script: Hindi uses Devanagari while Urdu uses an extended form of the Perso-Arabic script, typically in the Nastaʿlīq style.

On this grammar page, Hindustani is written in the transcription outlined in Masica (1991). Being "primarily a system of transliteration from the Indian scripts, [and] based in turn upon Sanskrit" (cf. IAST), these are its salient features: subscript dots for retroflex consonants; macrons for etymologically, contrastively long vowels; h for aspirated plosives; and tildes for nasalised vowels.

The sounds presented in parentheses in the tables below signify they are only found in loanwords from either Persian or Sanskrit. More information about phonology of Hindustani can be read on Hindustani phonology and IPA/Hindi and Urdu.

Hindustani natively possesses a symmetrical ten-vowel system. The vowels [ə], [ɪ], [ʊ] are always short in length, while the vowels [ɑː], [iː], [uː], [eː], [oː], [ɛː], [ɔː] are always considered long, in addition to an eleventh vowel /æː/ which is found in English loanwords.

[ɛ] occurs as a conditional allophone of /ə/ (schwa) in proximity to /ɦ/, if and only if the /ɦ/ is surrounded on both sides by two schwas. and is realised as separate vowel. For example, in kahanā /kəɦ(ə)naː/ (कहना – کَہنا 'to say'), the /ɦ/ is surrounded on both sides by schwa, hence both the schwas will become fronted to short [ɛ], giving the pronunciation [kɛɦɛnaː]. Syncopation of phonemic middle schwa can further occur to give [kɛɦ.naː].

Similarly, [ɔ] occurs as a conditional allophone of /ə/ and /ʊ/ in proximity to /ɦ/, specifically when they occur in the sequence /əɦʊ/, pronounced [ɔɦɔ]. For example, the word bahut /bəɦʊt/ (बहुत – بہت 'many') is pronounced [bɔɦɔt].

Hindustani has a core set of 28 consonants inherited from earlier Indo-Aryan. Supplementing these are two consonants that are internal developments in specific word-medial contexts, and seven consonants originally found in loan words, whose expression is dependent on factors such as status (class, education, etc.) and cultural register (Modern Standard Hindi vs Urdu).

[v] and [w] are allophones in Hindustani. These are distinct phonemes in English, but both are allophones of the phoneme /ʋ/ in Hindustani (written ⟨व⟩ in Hindi or ⟨و⟩ in Urdu), including loanwords of Arabic and Persian origin. More specifically, they are conditional allophones, i.e. rules apply on whether ⟨व⟩ is pronounced as [v] or [w] depending on context. Native Hindi speakers pronounce ⟨व⟩ as [v] in vrat (व्रत – ورت, 'vow') and [w] in pakwān (पकवान – پکوان 'food dish'), treating them as a single phoneme and without being aware of the allophonic distinctions, though these are apparent to native English speakers. The rule is that the consonant is pronounced as semivowel [w] in onglide position, i.e. between an onset consonant and a following vowel.