H. Wilberforce Clarke

“ When a consonant is accompanied by one of the three vowels, fatḥa, kasra, or ẓamma, it is said to be مُتَحَرِّك mutaḥarrik, or moveable.
⁠In Persian and Arabic, the first letter of a word is always accompanied, or moveable, by a vowel.When, in the middle or at the end of a word, a consonant is not accompanied by a vowel, it is said to be ساکن sākin, quiescent, or inert. Thus in the word مَرْدُم mardum, the م is moveable by fatḥa; the ر is inert, having no vowel ; د is moveable by ẓamma, and, finally, the م is inert. ”

“ When s and h, or z and h, represent two separate letters following each other, as in اسْهَل as,hal, " more or most easy' and اَزهار az,hār, "plants," a comma will be inserted, as shown in the examples. ”