Glottal consonants, also called laryngeal consonants, are consonants articulated with the glottis. Many phoneticians consider them, or at least the so-called fricatives, to be transitional states of the glottis without a point of articulation as other consonants have; in fact, some do not consider them to be consonants at all. However, the glottal stop at least behaves as a typical consonant in languages such as Tsou.
Glottal consonants in the International Phonetic Alphabet:
IPA Description Example
voiceless glottal stop
Hawaiian
‘okina
[ʔo.ˈki.na]
‘okina
breathy voiced glottal "fricative"
Czech
Praha
[ˈpra.ɦa]
Prague
voiceless glottal "fricative"
English
hat
[ˈhæt]
hat
The "fricatives" are not true fricatives. This is a historical usage of the word. They instead represent transitional states of the glottis (phonation) without a specific place of articulation. [h] is a voiceless transition. [ɦ] is a breathy-voiced transition, and could be transcribed as [h̤].
The glottal stop occurs in many languages. Often all vocalic onsets are preceded by a glottal stop, for example in German. The Hawaiian language writes the glottal stop as an opening single quote ‘. Some alphabets use diacritics for the glottal stop, such as hamza <ء> in the Arabic alphabet; in many languages of Mesoamerica, the Latin letter <h> is used for glottal stop.
Because the glottis is necessarily closed for the glottal stop, it cannot be voiced.