The glottal stop or “hamze” is a glottal consonant. It is articulated at the glottis, which is the opening between the vocal folds. Hamze is produced when the vocal cords are pressed together to stop the flow of air and then released. For example, the break separating the syllables of the interjection “uh-oh”. The glottal stop is present in nearly all dialects of English as a variant of /t/ e.g. button in American English.

The consonant “h” is another glottal consonant. Its place of articulation is glottis and only differs with hamze in the manner of articulation (fricative vs. plosive/stop). You can use “h” as a starting point to learn how to articulate hamze.

The glottal stop is found in many languages but there is no character for it in Latin alphabet because in most Indo-European languages, the glottal stop only occurs at the beginning of syllables. However in Persian, the glottal stop can occur anywhere in a word and therefore, it is marked in writing. It is usually marked with an apostrophe in educational books. However, the apostrophe is a “sign” and not a “letter”. Moreover, its standard function is to mark contractions:

Language Examples
English she’s (she + is)
can’t (can + not)
I’ve (I have)
French l’arbre (le + arbre)
c’est (ce + est)
Italian l’ora (la + ora)
po’ (poco)
German geht’s (geht + es)

The apostrophe can not be employed to denote both contractions and glottal stop. The glottal stop is a sound and just like the other sounds of Persian language, it should be denoted with a letter. The author proposes the letter “ø”. This leaves apostrophe to be exclusively used for contractions.

Persian Latin Contraction
ابری‌ست abrî’st abrî + ast
کجاست kojâ’st kojâ + ast
زین z’în ze + în