Voiceless glottal fricative

The voiceless glottal fricative, sometimes called voiceless glottal transition, and sometimes called the aspirate, is a type of sound used in some spoken languages that patterns like a fricative or approximant consonant phonologically, but often lacks the usual phonetic characteristics of a consonant. The symbol in the International Phonetic Alphabet that represents this sound is ⟨h⟩, and the equivalent X-SAMPA symbol is h.

Although [h] has been described as a voiceless vowel because in many languages, it lacks the place and manner of articulation of a prototypical consonant as well as the height and backness of a prototypical vowel:

[h and ɦ] have been described as voiceless or breathy voiced counterparts of the vowels that follow them [but] the shape of the vocal tract […] is often simply that of the surrounding sounds. […] Accordingly, in such cases it is more appropriate to regard h and ɦ as segments that have only a laryngeal specification, and are unmarked for all other features. There are other languages [such as Hebrew and Arabic] which show a more definite displacement of the formant frequencies for h, suggesting it has a [glottal] constriction associated with its production.

Lamé contrasts voiceless and voiced glottal fricatives.