Extensions to the IPA in the context of "Speech disorder"

Voiceless alveolar and dental plosives (or stops) are a type of consonantal sound used in almost all spoken languages. The symbol in the International Phonetic Alphabet that represents voiceless dental, alveolar, and postalveolar plosives is ⟨t⟩. The voiceless dental plosive can be distinguished with the underbridge diacritic, ⟨t̪⟩ and the postalveolar with a retraction line, ⟨t̠⟩, and the extIPA has a double underline diacritic which can be used to explicitly specify an alveolar pronunciation, ⟨t͇⟩.

The [t] sound is a very common sound cross-linguistically. Most languages have at least a plain [t], and some distinguish more than one variety. Some languages without a [t] are colloquial Samoan (which also lacks an [n]), Abau, and Nǁng of South Africa.

Unicode supports several phonetic scripts and notation systems through its existing scripts and the addition of extra blocks with phonetic characters. These phonetic characters are derived from an existing script, usually Latin, Greek or Cyrillic. Apart from the International Phonetic Alphabet (IPA), extensions to the IPA and obsolete and nonstandard IPA symbols, these blocks also contain characters from the Uralic Phonetic Alphabet and the Americanist Phonetic Alphabet.

Linguolabials or apicolabials are consonants articulated by placing the tongue tip or blade against the upper lip, which is drawn downward to meet the tongue. They represent one extreme of a coronal articulatory continuum which extends from linguolabial to subapical palatal places of articulation. Cross-linguistically, linguolabial consonants are very rare. They are found in a cluster of languages in Vanuatu, in the Kajoko dialect of Bijago in Guinea-Bissau, in Umotína (a recently extinct Bororoan language of Brazil), and as paralinguistic sounds elsewhere. They are also relatively common in disordered speech, and the diacritic is specifically provided for in the extensions to the IPA.

Linguolabial consonants are transcribed in the International Phonetic Alphabet by adding the "seagull" diacritic, U+033C ◌̼ COMBINING SEAGULL BELOW, to the corresponding alveolar or dental consonant. Pullum & Ladusaw (1996) additionally suggest these sound may be equivalently transcribed with the apical diacritic, U+033A ◌̺ COMBINING INVERTED BRIDGE BELOW, on the corresponding bilabial consonant. However, Olson et al. (2009:64) reject this transcription, as linguolabials may be articulated either apical or laminal. The labial consonants ⟨p᫥, m̼, v̼⟩ have also been used. The choice of the base consonant may depend on whether the author analyses the linguolabial as being phonologically labial or alveolar.

A dental consonant is a consonant articulated with the tongue against the upper teeth, such as /θ/, /ð/. In some languages, dentals are distinguished from other groups, such as alveolar consonants, in which the tongue contacts the gum ridge. Dental consonants share acoustic similarity and in the Latin script are generally written with consistent symbols (e.g. t, d, n).

In the International Phonetic Alphabet, the diacritic for dental consonant is U+032A ◌̪ COMBINING BRIDGE BELOW. When there is no room under the letter, it may be placed above, using the character U+0346 ◌͆ COMBINING BRIDGE ABOVE, such as in /p͆/. However, this has a different meaning in the Extensions to the IPA.