Editing International Phonetic Alphabet (section)

== Segments without letters ==
The blank cells on the summary IPA chart can be filled without much difficulty if the need arises.

The missing retroflex letters, namely {{angbr IPA|ᶑ ꞎ 𝼅 𝼈 𝼊&thinsp;}}, are "implicit" in the alphabet, and the IPA supported their adoption into Unicode.<ref name=pulmonic /> Attested in the literature are the [[retroflex implosive]] {{angbr IPA|ᶑ&thinsp;}}, the [[voiceless retroflex lateral fricative]] {{angbr IPA|ꞎ&thinsp;}}, the [[retroflex lateral flap]] {{angbr IPA|𝼈&thinsp;}} and the [[retroflex click]] {{angbr IPA|𝼊&thinsp;}}; the first is also mentioned in the IPA ''Handbook'', and the lateral fricatives are provided for by the [[extIPA]].

The epiglottal trill is arguably covered by the generally trilled epiglottal "fricatives" {{angbr IPA|ʜ ʢ}}. Ad hoc letters for near-close central vowels, {{angbr IPA|ᵻ ᵿ}}, are used in some descriptions of English, though those are specifically [[reduced vowels]]{{snd}}forming a set with the IPA reduced vowels {{angbr IPA|ə ɐ}}{{snd}}and the simple points in vowel space are easily transcribed with diacritics: {{angbr IPA|ɪ̈ ʊ̈}} or {{angbr IPA|ɨ̞ ʉ̞}}. Diacritics are able to fill in most of the remainder of the charts.{{NoteTag|"Diacritics may also be employed to create symbols for phonemes, thus reducing the need to create new letter shapes."<ref>{{harv|International Phonetic Association|1999|p=27}}</ref>}} If a sound cannot be transcribed, an asterisk {{angbr IPA|*}} may be used, either as a letter or as a diacritic (as in {{angbr IPA|k*}} sometimes seen for the [[Korean phonology|Korean]] "fortis" velar).

=== Consonants<!--subheading 2--> ===
Representations of consonant sounds outside of the core set are created by adding diacritics to letters with similar sound values. The Spanish bilabial and dental approximants are commonly written as lowered fricatives, {{IPA|[β̞]}} and {{IPA|[ð̞]}} respectively.{{NoteTag|note=Dedicated letters have been proposed, such as rotated <span style="{{mirrorH}}; {{mirrorV}};">{{angbr IPA|β}}</span> and <span style="{{mirrorH}}; {{mirrorV}};">{{angbr IPA|ð}}</span>, reversed <span style="{{mirrorH}}">{{angbr IPA|β}}</span> and <span style="{{mirrorH}}">{{angbr IPA|ð}}</span>, or small-capital {{angbr IPA|{{sm|б}}}} and {{angbr IPA|ᴆ}}. Ball, Rahilly & Lowry (2017) ''Phonetics for speech pathology'', 3rd edition, Equinox, Sheffield.}} Similarly, voiced lateral fricatives can be written as raised lateral approximants, {{IPA|[ɭ˔ ʎ̝ ʟ̝]}}, though the extIPA also provides {{angbr IPA|𝼅}} for the first of these. A few languages such as [[Banda languages|Banda]] have a bilabial flap as the preferred allophone of what is elsewhere a labiodental flap. It has been suggested that this be written with the labiodental flap letter and the advanced diacritic, {{IPA|[ⱱ̟]}}.<ref>{{cite journal |last1=Olson |first1=Kenneth S. |last2=Hajek |first2=John |year=1999 |title=The phonetic status of the labial flap |journal=Journal of the International Phonetic Association |volume=29 |issue=2 |pages=101–114 |doi=10.1017/s0025100300006484 |s2cid=14438770}}</ref>
Similarly, a labiodental trill would be written {{IPA|[ʙ̪]}} (bilabial trill and the dental sign), and the labiodental plosives are now universally {{angbr IPA|p̪ b̪}} rather than the ''ad hoc'' letters {{angbr IPA|ȹ ȸ}} once found in Bantuist literature. Other taps can be written as extra-short plosives or laterals, e.g. {{IPA|[&thinsp;ɟ̆ ɢ̆ ʟ̆]}}, though in some cases the diacritic would need to be written below the letter. A [[retroflex trill]] can be written as a retracted {{IPA|[r̠]}}, just as non-subapical retroflex fricatives sometimes are. The remaining pulmonic consonants – the uvular laterals ({{IPA|[ʟ̠ 𝼄̠ ʟ̠˔]}}) and the palatal trill – while not strictly impossible, are very difficult to pronounce and are unlikely to occur even as allophones in the world's languages.

=== Vowels<!--subheading 2--> ===
The vowels are similarly manageable by using diacritics for raising, lowering, fronting, backing, centering, and mid-centering.{{NoteTag|"The diacritics...can be used to modify the lip or tongue position implied by a vowel symbol."<ref>{{harv|International Phonetic Association|1999|p=16}}</ref>}} For example, the unrounded equivalent of {{IPA|[ʊ]}} can be transcribed as mid-centered {{IPA|[ɯ̽]}}, and the rounded equivalent of {{IPA|[æ]}} as raised {{IPA|[ɶ̝]}} or lowered {{IPA|[œ̞]}} (though for those who conceive of vowel space as a triangle, simple {{IPA|[ɶ]}} already is the rounded equivalent of {{IPA|[æ]}}). True mid vowels are lowered {{IPA|[e̞ ø̞ ɘ̞ ɵ̞ ɤ̞ o̞]}} or raised {{IPA|[ɛ̝ œ̝ ɜ̝ ɞ̝ ʌ̝ ɔ̝]}}, while centered {{IPA|[ɪ̈ ʊ̈]}} and {{IPA|[ä]}} (or, less commonly, {{IPA|[ɑ̈]}}) are near-close and open central vowels, respectively.

The only known vowels that cannot be represented in this scheme are vowels with unexpected [[roundedness]]. For unambiguous transcription, such sounds would require dedicated diacritics. Possibilities include {{angbr IPA|ʏʷ}} or {{angbr IPA|ɪʷ}} for protrusion and {{angbr IPA|uᵝ}} (or VoQS {{angbr IPA|ɯᶹ}}) for compression. However, these transcriptions suggest that the sounds are diphthongs, and so while they may be clear for a language like Swedish where they are diphthongs, they may be misleading for languages such as Japanese where they are monophthongs.
The [[extIPA]] 'spread' diacritic {{angbr IPA|◌͍}} is sometimes seen for compressed {{angbr IPA|u͍}}, {{angbr IPA|o͍}}, {{angbr IPA|ɔ͍}}, {{angbr IPA|ɒ͍}}, though again the intended meaning would need to be explained or they would be interpreted as being spread the way that cardinal {{IPA|⟦i⟧}} is. For protrusion (''w''-like labialization without velarization), Ladefoged & Maddieson use the old IPA omega diacritic for labialization, {{angbr IPA|◌̫}}, for protruded {{angbr IPA|y᫇}}, {{angbr IPA|ʏ̫}}, {{angbr IPA|ø̫}}, {{angbr IPA|œ̫}}. This is an adaptation of an old IPA convention of rounding an unrounded vowel letter like ''i'' with a subscript omega ({{angbr IPA|◌̫}}) and unrounding a rounded letter like ''u'' with a subscript turned omega.<ref>{{Cite book |last1=Jespersen |first1=Otto |author1-link=Otto Jespersen |last2=Pedersen |first2=Holger |author2-link=Holger Pedersen (linguist) |year=1926 |page=19 |title=Phonetic Transcription And Transliteration, Proposals Of The Copenhagen Conference, April 1925 |publisher=Clarendon |url=https://archive.org/details/jespersen-pedersen-1926-phonetic-transcription-and-transliteration}}</ref>
{{as of|2024}}, the turned omega diacritic is in the pipeline for Unicode, and is under consideration for compression in extIPA.<ref>[https://www.unicode.org/L2/L2024/24080-ipa-diacritics-above.pdf L2/24-080]</ref>
Kelly & Local use a combining ''w'' diacritic {{angbr IPA|◌ᪿ}} for protrusion (e.g. {{angbr IPA|yᷱ øᪿ}}) and a combining ''ʍ'' diacritic {{angbr IPA|◌ᫀ}} for compression (e.g. {{angbr IPA|uᫀ oᫀ}}).<ref>{{harvnb|Kelly|Local|1989|p=154}}</ref> Because their transcriptions are manuscript, these are effectively the same symbols as the old IPA diacritics, which indeed are historically cursive ''w'' and ''ʍ''. However, the more angular {{angbr IPA|◌ᫀ}} of typescript might misleadingly suggest the vowel is protruded and voiceless (like {{IPA|[ʍ]}}) rather than compressed and voiced.