Is it correct to say or write an student or an store?
- Anybody can ask a question
- Anybody can answer
- The best answers are voted up and rise to the top
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.
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.
When speaking it is appropriate to say
When writing you may use:
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.