Officially, yes. Most teachers/professors will accept it either way. ANSWER In American English, it depends on whether or not the "h" is sounded. In "hour," it is not sounded; therefore, we say, "an hour." In "hostage," it is sounded; therefore, we say, "a hostage." [Some U.S.A. dialects use "a" in some words even when the "h" is not sounded. In the South, for example, one hears, "I'll be back in a (h)our."] That view rests on the general rule that if a word begins with a vowel we use "an," if it begins with a consonant, we use "a." Some h-words have alternate pronunciations, with the h and without. For example, the word "homage" is homage or omage -- or, in modern film lingo "ohMAGE." In America, we would say, "a homage"; "an omage"; "an ohMAGE." [spelvin]