Anusvara (Sanskrit: अनुस्वार anusvāra) is a symbol used in many Indic scripts to mark a type of nasal sound, typically transliterated ⟨ṃ⟩. Depending on its location in the word and the language for which it is used, its exact pronunciation can vary. In the context of ancient Sanskrit, anusvara is the name of the particular nasal sound itself, regardless of written representation.

In Vedic Sanskrit, the anusvāra (lit. "after-sound" or "subordinate sound")^[2] was an allophonic (derived) nasal sound.

The exact nature of the sound has been subject to debate.

The material in the various ancient phonetic treatises points towards different phonetic interpretations, and these discrepancies have historically been attributed to either differences in the description of the same pronunciation^[3] or to dialectal or diachronic variation.^[4][5] In a 2013 reappraisal of the evidence, Cardona concludes that these reflect real dialectal differences.^[6]

The environments in which the anusvara could arise, however, were well defined.

In the earliest Vedic Sanskrit, it was an allophone of /m/ at a morpheme boundary, or of /n/ within morphemes, when it was preceded by a vowel and followed by a fricative (/ś/, /ṣ/, /s/, /h/).^[2] In later Sanskrit its use expanded to other contexts, first before /r/ under certain conditions, then, in Classical Sanskrit, before /l/ and /y/.^[2] Later still, Pāṇini gave anusvara as an alternative pronunciation in word-final sandhi, and later treatises also prescribed it at morpheme junctions and within morphemes.^[7] In the later written language, the diacritic used to represent anusvara was optionally used to indicate a nasal stop having the same place of articulation as a following plosive.

In the Devanagari script, anusvara is represented with a dot (bindu) above the letter (e.g. मं). In the International Alphabet of Sanskrit Transliteration (IAST), the corresponding symbol is ṃ (m with an underdot). Some transcriptions render notation of phonetic variants used in some Vedic shakhas with variant transcription (ṁ).

In writing Sanskrit, the anusvara is often used as an alternative representation of the nasal stop with the same place of articulation as the following plosive.

For example, [əŋɡə] 'limb (of the body)' may be written with either a conjunct, अङ्ग aṅga, or with an anusvara, अंग aṃga. A variant of the anusvara, the anunāsika or 'candrabindu', was used more explicitly for nasalized vowels, as in अँश aṃśa for [ə̃ɕə] 'portion'.^[8]

In Standard Hindi, the anusvāra is traditionally defined as representing a nasal consonant homorganic to a following plosive, in contrast to the candrabindu (anunāsika), which indicates vowel nasalization. In practice, however, the two are often used interchangeably.

The precise phonetic value of the phoneme, whether it is represented by anusvāra or candrabindu, is dependent on the phonological environment.^[9]

Word-finally it is realized as nasalization of the preceding vowel: kuāṃ [kʊ̃ãː], "a well". It results in vowel nasalization also medially between a short vowel and a non-obstruent (kuṃvar [kʊ̃ʋər] "a youth", gaṃṛāsā [ɡə̃ɽaːsaː] "a long-handled axe") and, in native words, between a long vowel and a voiceless plosive (dāṃt [dãːt] "tooth", sāṃp [sãːp] "a snake", pūṃch [pũːtʃʰ] "tail").

It is pronounced as a homorganic nasal, with the preceding vowel becoming nasalized allophonically, in the following cases: between a long vowel and a voiced plosive (tāṃbā [taːmbaː] "copper", cāṃdī [tʃaːndiː] "silver"), between a long vowel and a voiceless plosive in loanwords (dāṃt [daːnt] "repressed", baiṃk [bæːŋk] "a bank", khazāṃcī [kʰəzaːɲtʃiː]), and between a short vowel and an obstruent (saṃbhāl- [səmbʱaːl] "to support", saṃdūk [sənduːk] "a chest").

The last rule has two sets of exceptions where the anusvāra effects only a nasalization of the preceding short vowel. Words from the first set are morphologically derived from words with a long nasalized vowel (baṃṭ- [bə̃ʈ], "to be divided" from bāṃṭ- [bãʈ], "to divide"; siṃcāī [sɪ̃tʃai], "irrigation" from sīṃc- [sĩːtʃ], "to irrigate"). In suchs cases, the vowel is sometimes denasalized ([bəʈ], [sɪtʃai] instead of [bə̃ʈ-], [sɪ̃tʃai]). The second set is composed of a few words like * (pahuṃc-* [pahʊ̃tʃ], "to arrive" and haṃs- [hə̃s], "to laugh").^[1]

In Marathi the anusvara is pronounced as a nasal that is homorganic to the following consonant (with the same place of articulation). For example, it is pronounced as the dental nasal न् before dental consonants, as the bilabial nasal म् before bilabial consonants, etc.

In Nepali, chandrabindu and anusvara have the same pronunciation similarly to Hindi. Therefore, there is a great deal of variation regarding which occurs in any given position. Many words containing anusvara thus have alternative spellings with chandrabindu instead of anusvara and vice versa.

Anusvara is used in other languages using Indic scripts as well, usually to represent suprasegmental phones (such as phonation type or nasalization) or other nasal sounds.

In the Bengali script, the anusvara diacritic (অনুস্বার onushshar in Bengali) is written as a circle above a slanted line (ং), and represents /ŋ/. It is used in the name of the Bengali language বাংলা [baŋla]. It has merged in pronunciation with the letter ঙ ungô in Bengali. Although the anusvara is a consonant in Bengali phonology, it is nevertheless treated in the written system as a diacritic in that it is always directly adjacent to the preceding consonant, even when consonants are spaced, apart in titles or banners: বাং-লা-দে-শ bang-la-de-sh, not বা-ং-লা-দে-শ ba-ng-la-de-sh for বাংলাদেশ Bangladesh It is never pronounced with the inherent vowel "ô", and it cannot take a vowel sign (instead, the consonant ঙ ungô is used pre-vocalically).

In the Burmese script, the anusvara (အောက်မြစ် auk myit IPA: [aʊʔ mjɪʔ]) is represented as a dot underneath a nasalised final to indicate a creaky tone (with a shortened vowel). Burmese also uses a dot above to indicate the /-ɴ/ nasalized ending (called "Myanmar Sign Anusvara" in Unicode), called သေးသေးတင် thay thay tin (IPA: [θé ðé tɪ̀ɴ])

In the Sinhala script, the anusvara is not a nonspacing combining mark but an spacing combining mark. It has circular shape and follows its base letter ( ං).^[10] It is called binduva in Sinhala, which means "dot". The anusvara represents /ŋ/ at the end of a syllable. It is used in the name of the Sinhala language සිංහල [ˈsiŋɦələ]. It has merged in pronunciation with the letter ඞ ṅa in Sinhala.

The Telugu script has full-zero (anusvāra) ం, half-zero (arthanusvāra) and visarga to convey various shades of nasal sounds. Anusvara is represented as a circle shape after a letter:^[11] క - ka and కం - kam.

The equivalent of the anusvara in the Thai alphabet is the nikkhahit, which is used when rendering Sanskrit and Pali texts. It is written as an open circle above the consonant (for example อํ) and its pronunciation depends on the following sound: if it is a consonant then the nikkhahit is pronounced as a homorganic nasal, and if it is at the end of a word it is pronounced as the velar nasal ŋ.

Anunasika (anunāsika) is a form of vowel nasalization, often represented by an anusvara. It is a form of open mouthed nasalization, akin to the nasalization of vowels followed by "n" or "m" in Parisian French. When "n" or "m" follow a vowel, the "n" or "m" becomes silent and causes the preceding vowel to become nasal (pronounced with the soft palate extended downward so as to allow part or all of the air to leave through the nostrils). Anunasika is sometimes called a subdot because of its IAST representation.

In Devanagari and related orthographies, it is represented by the chandrabindu diacritic (example: मँ ).

In Burmese, the anunasika, called သေးသေးတင် (IPA: [θé ðé tɪ̀ɴ]) and represented as (ံ), creates the /-ɴ/ nasalized ending when it is attached as a dot above a letter. The anunasika represents the -m final in Pali.

Unicode encodes anusvara and anusvara-like characters for a variety of scripts: