“a” or “an” for words that don't start with vowels but sound like they're starting with a vowel

Question

Is it correct to say or write an student or an store?

Answer 1

Always use an for words which sound like they start with a vowel, and always use a for words which sound like they start with a consonant. The rules for h are more complex, and it can be ok to use either.

The usage of the indefinite article preceding h are discussed here. In particular, look at nohat's response.

As for student and store, they should always be preceded with a and never with an, because they both start with the consonant /s/ when spoken.

Correct:

A student, a store

Incorrect:

An student, an store

Answer 2

The quickest way to remember the rule for this: "an hour and a half". Thus, "a" for something with an initial consonant sound, and "an" otherwise.

Answer 3

When speaking it is appropriate to say

an hour.

When writing you may use:

a hour.

provided you use it consistently. In text containing a large amount of dialogue it could be more appropriate to use 'an' to imitate the manner of someone speaking.