M̃

M̃ (majuscule: M̃, minuscule: m̃) is a Latin M with a diacritical tilde.

The characters “M̃” (uppercase) and “m̃” (lowercase) consist of the Latin letter M with a combining tilde diacritic (U+0303), represented in Unicode as U+004D or U+006D followed by U+0303 to ensure broad compatibility across digital platforms.^[1] While precomposed forms of M̃ are not included in the primary Latin-1 supplement, these combining sequences enable accurate rendering in HTML (e.g., “M̃”) and LaTeX (via \verb|~{M}|).^[2] Input methods on major operating systems — such as Windows’s US International keyboard, macOS’s Option + n dead key, and Linux compose-key sequences — support the combining tilde with minimal configuration.

In linguistics, M̃ appears chiefly in phonetic transcription and the orthographies of a few languages and dialects to denote features such as nasalization, denasalization or secondary articulation. It is used in the International Phonetic Alphabet for denasalized consonants and specialized Americanist notations for unreleased or partially nasal segments .^[3] Minority and constructed languages employing M̃ include certain notations of Proto-Indo-European reconstructions, Mapudungun phonemic studies, and some orthographies of Central American indigenous languages; in these contexts, it is typically called “m tilde” and occurs infrequently relative to other diacritic combinations.

M̃–m̃ is or was used as a grapheme in several languages:

• in some languages of Vanuatu, such as North Efate, South Efate and Namakura, it represents a labial-velar nasal [ŋ͡m]. The letter was introduced by missionaries and has been in use for over a hundred years. (Other Vanuatu languages use an M-macron (m̄) instead.)
• in the Yanesha' language of Peru, m̃ represents a palatalized m
• in Lithuanian, m̃ appears as part of diphthongs
• in the transliteration of the Lycian script, it represents a syllabic m.

In Italian, the abbreviation Ssm̃o or SSm̃o may be used for Santissimo, "most holy" (similarly Latin Ssm̃us for Sanctissimus).

M̃ and m̃ are used in mathematics and physics, see Tilde#Mathematics and Tilde#Physics

Characters consisting of the base letter M or m followed by a combining tilde mark are used in digital encoding systems rather than as single precomposed characters.

In Unicode, both uppercase and lowercase forms are represented with the base letter followed by the combining tilde (U+0303): Uppercase: U+004D (Latin capital letter M) + U+0303 (combining tilde) Lowercase: U+006D (Latin small letter m) + U+0303 (combining tilde)^[1]

In HTML and XML, combining tildes may be encoded either by numeric character references or by named entities for the combining mark:^[4]

 M̃ → M̃ or M̃ m̃ → m̃ or m̃ 

In LaTeX, the tilde diacritic can be applied using the \verb|~{}| command:^[2]

 \~{M} produces Ṁ (uppercase M̃) \~{m} produces ṁ (lowercase m̃) 

Common input methods on major operating systems vary.

Windows: use the US International keyboard layout and type \verb|~| followed by \verb|m| or \verb|M|.

macOS: press Option + n to register the tilde accent, then type \verb|m| or \verb|M|. On the Apple ABC extended keyboard, m̃ is made by typing m and then option-shift n.

Linux: with a Compose key, press Compose, \verb|~|, \verb|m|.| These methods ensure consistent rendering of M̃ and m̃ across applications and platforms.