word choice - "An hour" or "a hour"

Which indefinite article should precede hour — a or an?

• an hour


• a hour

Does the usage of an vs a depend on the pronunciation — a history, a hobby, but an hour, an honor?

Answer

Does the usage of an vs a depends on the pronunciation: a history, a hobby, but an hour, an honor.

Yes. If a word begins with a vowel sound, then the correct article is an; otherwise, if it begins with a consonantal sound, the correct article is a.

Because hour is typically pronounced with a silent h, an hour is correct.

I wrote a blog post about an vs a on the EL&U blog some time ago, and it covers a wide variety of other cases that you might be interested in.