Click
From KneeQuickie
More properly known as velaric (or uvular) ingressive stops, clicks are a class of rare phonemes called so for their abrupt, percussive sound that usually resemble a click or snap. Clicks are necessarily doubly articulated, involving both a dorsal closure, often known as the accompaniment, and a coronal or (more rarely) a labial closure. They function on a unique velaric ingressive airstream mechanism in which pressure builds between the two closures, producing the signature click when released due to air rushing into the opened space.
Despite their often formidable complexity, clicks have often been characterized as crude and primitive phonemes in the past, with hints of derision that arguably persist to this day.
Front articulation
All clicks have a front closure that when released creates their characteristic clicking sound. There are a number of possible front closures, all of them coronal or bilabial, with each resulting a different type of click. Contrary to widespread belief, no attested clicks use a velar front articulation and there is no evidence that any such clicks have ever existed.
Dorsal articulation
Writing clicks
The IPA has three symbols for coronal clicks, but it is not agreed exactly what their meaning is. In some IPA charts, /ǀ/ is given as a dental click, /ǂ/ as alveolar, and /ǃ/ as retroflex; in others, /ǀ/ is given as dental, /ǂ/ as palatoalveolar, and /ǃ/ as alveolar or postalveolar.
Linguists transcribing the Khoi and Bushman languages generally use the IPA symbols, combined with normal letters in polygraphs to indicate accompaniments.
Orthographies for Bantu languages such as Xhosa and Zulu generally reuse c, q, and x to write dental, alveolar, and lateral clicks respectively. As with the Khoisan languages, digraphs are used to indicate accompaniments.
This difference probably arises to meet the desires of the few natlangs that use clicks. In some languages, there is no postalveolar click, so the symbol is used for the retroflex click; no language contrasts the two, so separate symbols are not needed. (This is why Z-Sampa explicitly states that the symbol can be used for both; see below.)
The second method above is endorsed by X-Sampa, which has the symbols /|\/, /=\/ and /!\/ respectively for the three clicks.
In Z-Sampa, the symbols are redefined to compromise between the two systems. Thus, /|\/ is still dental, /=\/ is alveolo-palatal or palatal, and /!\/ is postalveolar or retroflex. To avoid confusion, /=\/ cannot be used for an alveolar click; the dental click symbol must be used, modified with the alveolar diacritic _a\. (But true alveolar clicks are a rarity in natlangs; they usually merge with the retroflex click.)
Z-Sampa offers an alternative transcription for clicks (see Clicks in Z-Sampa) based on modifying the corresponding plosive with the click diacritic _!. Thus, /t_!/, /c_!/ and /t`_!/ are the same as /|\/, /=\/ and /!\/ respectively.
Note in particular that although /t/ is normally assumed to be alveolar by default, and must be modified with a diacritic to specify a dental /t/, the exact reverse is true for its corresponding click /t_!/.
