In English, ⟨h⟩ occurs as a single-letter grapheme (being either silent or representing the voiceless glottal fricative (/h/) and in various digraphs, such as ⟨ch⟩ /tʃ/, /ʃ/, /k/, or /x/), ⟨gh⟩ (silent, /ɡ/, /k/, /p/, or /f/), ⟨ph⟩ (/f/), ⟨rh⟩ (/r/), ⟨sh⟩ (/ʃ/), ⟨th⟩ (/θ/ or /ð/), ⟨wh⟩ (/hw/ ). The letter is silent in a syllable rime, as in ah, ohm, dahlia, cheetah, pooh-poohed, as well as in certain other words (mostly of French origin) such as hour, honest, herb (in American but not British English) and vehicle (in certain varieties of English). Initial /h/ is often not pronounced in the weak form of some function words including had, has, have, he, her, him, his, and in some varieties of English (including most regional dialects of England and Wales) it is often omitted in all words (see '⟨h⟩'-dropping). It was formerly common for an rather than a to be used as the indefinite article before a word beginning with /h/ in an unstressed syllable, as in "an historian", but use of a is now more usual (see English articles § Indefinite article). In English, The pronunciation of ⟨h⟩ as /h/ can be analyzed as a voiceless vowel. That is, when the phoneme /h/ precedes a vowel, /h/ may be realized as a voiceless version of the subsequent vowel. For example the word ⟨hit⟩, /hɪt/ is realized as [ɪ̥ɪt]. H is the eighth most frequently used letter in the English language (after S, N, I, O, A, T, and E), with a frequency of about 4. 2% in words.