Nuqta

The nuqta (नुक़्ता, nuqtā; sometimes also spelled nukta), is a diacritic mark that was introduced in Devanagari and some other Indic scripts to represent sounds not present in the original scripts. It takes the form of a dot placed below a character. This idea is inspired from the Arabic script; for example, there are some letters in Urdu that share the same basic shape but differ in the placement of dots(s) or nuqta(s) in the Perso-Arabic script: the letter ع ayn, with the addition of a nuqta on top, becomes the letter غ g͟hayn.

Perso-Arabic consonants
The term (नुक़्ता) is itself an example of the use of the nuqta (making it autological.) Other examples include क़िला; and आग़ा ख़ान, a combination of a Perso-Arabic (āġā) and a Türko-Mongolic (k͟hān) honorific.

The nuqta, and the phonological distinction it represents, is sometimes ignored in practice; e.g., क़िला being simply spelled as किला. In the text Dialect Accent Features for Establishing Speaker Identity, Manisha Kulshreshtha and Ramkumar Mathur write, "A few sounds, borrowed from the other languages like Persian and Arabic, are written with a dot (bindu or nuqtā). Many people who speak Hindi as a second language, especially those who come from rural backgrounds and do not speak conventional Hindi (also called Khaṛībōlī), or speak in one of its dialects, pronounce these sounds as their nearest equivalents." For example, these rural speakers will assimilate the sound ɣ (Devanagari: ग़; Nastaliq: ) as ɡ (Devanagari: ग; Nastaliq: ).

With a renewed Hindi–Urdu language contact, many Urdu writers now publish their works in Devanagari editions. Since the Perso-Arabic orthography is preserved in Nastaʿlīq script Urdu orthography, these writers use the nuqta in Devanagari when transcribing these consonants.

Dravidian consonants
Devanagari also includes coverage for the Dravidian consonants ऴ /ɻ/; ऱ /r/ and ऩ /n/. (Respectively, these letters modify ळ /ɭ/; र /ɾ/ and न /n̪/). An example is तमिऴ् /t̪amiɻ/ (தமிழ்).

Dardic consonants
For example, the letters च़ and छ़ are used in Devanagari to write the Kashmiri alveolar affricates  and   respectively.

Eastern Indo-Aryan letters
To represent the Eastern Nagari letter য় representing /ɔ/, the consonant य़ is used in Devanagari.

In Maithili, there are four non-syllabic vowels: i̯, u̯, e̯, o̯ written in Devanagari as य़, व़, य़ॆ, व़ॊ. But colloquially, these are written without nuqta.

The Bengali-Assamese script has ড় ঢ় য়, which are variations of ড ঢ য; however, ব and র are completely different in nature.

Similar diacritics
Sindhi's and Saraiki's implosives are accommodated in Devanagari with a line attached below—a diacritical bar: ॻ, ॼ , ॾ , ॿ.

In Tamil script, the special character ஃ (ஆய்த எழுத்து, ) is used like nuqta to represent non-native consonants.

In Thaana script of Maldives, one or many nuqtas are added to their native consonants to represent Perso-Arabic consonants, and each phoneme is encoded as a whole in the Unicode block (instead of a separate codepoint for the diacritic).