I believe that you use 'an' only if there is a vowel (a, e, i, o and u.... But you know that), and h is not a vowel.)
Opinion is divided over the form to use before h-words in which the first syllable is unstressed: the thoroughly modern thing to do is to use a (never an) together with an aspirated h (a habitual, a heroic, a historical, a Homeric, a hypothesis), but not to demur if others use an . . .
It used to be that you used an before an aspirated (pronounced) h IF the first syllable of the h- word wasn't accented. That's why you'll hear some people say "It was an historical day" but "I've written a history of the world." His-TOR-i-cal stresses the second syllable, wheras HIS-tor-y stresses the first.
So if you followed that practice, you'd say "a hierarchy" but "an hierarchical arrangement."
But that practice is passing away, I think, and the rule that's already been mentioned (a for the aspirated h and an for the silent h) is the one to follow.
Here's what Fowler's says:
Nancy Holzner
What matters is not how we pronounce our words, but how the reader is going to pronounce our words, thus the rules should be in place universally...
What matters is not how we pronounce our words, but how the reader is going to pronounce our words, thus the rules should be in place universally.
It used to be that you used an before an aspirated (pronounced) h IF the first syllable of the h- word wasn't accented. That's why you'll hear some people say "It was an historical day" but "I've written a history of the world." His-TOR-i-cal stresses the second syllable, wheras HIS-tor-y stresses the first.
So if you followed that practice, you'd say "a hierarchy" but "an hierarchical arrangement."
But that practice is passing away, I think, and the rule that's already been mentioned (a for the aspirated h and an for the silent h) is the one to follow.
It used to be that you used an before an aspirated (pronounced) h IF the first syllable of the h- word wasn't accented. That's why you'll hear some people say "It was an historical day" but "I've written a history of the world." His-TOR-i-cal stresses the second syllable, wheras HIS-tor-y stresses the first.
So if you followed that practice, you'd say "a hierarchy" but "an hierarchical arrangement."
But that practice is passing away, I think, and the rule that's already been mentioned (a for the aspirated h and an for the silent h) is the one to follow.