Glottal consonant

A glottal consonant is a sound made using only the glottis. English has two glottal consonants, [h], as in hat and [ʔ], as in uh-oh.
The International Phonetic Alphabet has symbols for three glottal consonants:
[h] and [ɦ] often are not true fricatives, and are more similar to voiceless vowels.