Request for IPA symbols: ɝ, Chao tone letters, standalone diacritics, tie bar, superscripts

U+025D ɝ is used in English transcriptions to indicate the American pronunciation of the vowel in _nurse_ /nɝːs/ and _term_ /tɝːm/.

U+02E5–U+02E9 ˥ ˦ ˧ ˨ ˩ are a set of tone letters designed by Yuen Ren Chao in the 1920s and adopted officially by the IPA in 1989, though they had been used continuously since their inception. There is also a set of reversed tone letters at U+A712–U+A716 ꜒ ꜓ ꜔ ꜕ ꜖; these are unofficial and mostly restricted to Chinese works. Note that sequences of tone letters form mandatory ligatures: ˧ + ˥ = ˧˥; ˨ + ˩ + ˦ = ˨˩˦.

U+02D2–U+02D7 ˒ ˓ ˔ ˕ ˖ ˗ are non-combining forms of a set of diacritics for relative articulation. They can be used when the base glyph has a descender (Spanish _algo_ [ˈalɣ˕o], _hoyo_ [ˈoʝ˕o]), or when transcribing a single segment ([e˔], [a˗], etc.)

The IPA tie bar is not a virāma, that is, it doesn’t form ligatures. There are many ways of transcribing affricates using the IPA ([ts t͡s t͜s ʦ tˢ] etc.), and while they usually stand for the same class of sounds, they’re not simply glyph variants of each other. The [latest version of the IPA chart](https://www.internationalphoneticassociation.org/IPAcharts/IPA_chart_orig/pdfs/IPA_Kiel_2020_full.pdf) actually endorses the use of “two symbols joined by a tie bar if necessary”. As an analogous case, [ɪ ʊ] and [ɩ ɷ] stand for the same vowels, the ones in _kit_ and _foot_, but they’re very explicitly not unified by Unicode and shouldn’t be given the same glyphs. Similarly, the tie bar is also often used for diphthongs, but [a͡e] (= [ae̯], similar to the vowel in _sky_) is _not_ the same as [æ] (the vowel in _cat_). If a ligature is desired, there are explicit codepoints for them: U+02A3–U+02A7 ʣ ʤ ʥ ʦ ʧ ʨ and U+AB66–U+AB67 ꭦ ꭧ. In any case, the [Library of Congress romanization of Russian](https://www.loc.gov/catdir/cpso/romanization/russian.pdf) transliterates the letter ц as ⟨t͡s⟩, and is incompatible with automatic IPA ligation.

There is a longstanding tradition of using superscript IPA symbols to indicate secondary articulations or shades of sound that can’t otherwise be represented. In English dictionaries, they often indicate optional sounds. Some of the more common ones that aren’t currently supported are:
* U+1D51 ᵑ for nasal clicks [ᵑǀ ᵑǁ ᵑǃ ᵑǂ] and prenasalized consonants such as [ᵑɡ]. It can take a ring above in sequences such as [ᵑ̊ǀʰ], and a tie bar in [ᵑ͡ᵐɡ͡b].
* U+1DAC ᶬ and U+1DAE ᶮ for prenasalized consonants such as [ᶬv ᶮɟ].
* U+1D5D ᵝ for compressed vowels such as the Japanese _u_ [ɯᵝ].
* U+1DB4 ᶴ and U+1DBE ᶾ for one way of transcribing affricates: [tᶴ dᶾ].
* U+02B4–U+02B6 ʴ ʵ ʶ for r-coloured vowels.