Characteristics
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. is a voiceless transition. is a breathy-voiced transition, and could be transcribed as .
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, while in Maltese, the letter ⟨q⟩ is used instead.
Because the glottis is necessarily closed for the glottal stop, it cannot be voiced.
Read more about this topic: Glottal Consonant