Articles: A, An

The difference between a and an is not grammatical, but is simply based on sound. Use a before every consonant, unless this consonant is part of an acronym where the letter in the acronym has a vowel sound (e.g. F = eff, M = em, N = en).

an is used before u, if the u is pronounced as in uncle, understanding, uninteresting.

a is used before u, if the sound is like you e.g. university, unique, utility

a is used before eu

a is used before h except in these cases: an hour, an honor, an honest, an heir

a and an are called ‘indefinite articles’. All countable nouns in the singular require an article (either a / an or the). You cannot say, for example, I am without ticket. But instead you should say I don’t have a ticket or the ticket.

If a noun is uncountable, then a / an are not used. You cannot say I need an information, instead you can use some or a piece of or in some cases simply omit the article.