Apical

From KneeQuickie

An apical consonant is one whose primary articulation is made with the tip of the tongue (the apex), as opposed to the lamina (blade) or dorsum.

All dental and linguolabial consonants are considered to be apical by default; the laminal equivalents are called interdentals and interlinguolabials respectively. Alveolar consonants can be either apical or laminal; for example, /s/ is laminal in English but apical in Castilian Spanish. Some languages, such as Basque, even contrast apical and laminal sounds at the same place of articulation: <s> represents the apical /s/ and <z> its laminal counterpart. (There is no voicing distinction between the two.) Basque also has affricates <ts> (apical) and <tz> (laminal).

Consonants further back in the mouth cannot be apical unless the tongue is curled backwards; consonants formed this way are called retroflex.

In the IPA, consonants can be marked as apical with a diacritic: for example, /s̺/ is apical /s/. The X-Sampa equivalent is _a.