Is Harvard a university or an university? We assume that the use of indefinite articles such as "a" and "an" is pretty straightforward - you use "a" in front of words beginning with a consonant and "an" in front of words beginning with a vowel (a, e, i, o, u), as in:

a cat
an egg

This is, of course, a good rule to follow, but unfortunately, it is not always right! If we go back to the word "university", we would assume the correct indefinite article is "an" as in "an university". But guess what? The correct term is "a university". Confused? Well, let's look at how to use "a" and "an" in more detail.

The use of a or an actually depends on how the word is pronounced - its phonetic sound. So, how you say a word will affect which article you use. The "u" in university is pronounced as "yew" (it sounds like a long "u") which means that although the letter is spelt using a vowel, it is pronounced like the first letter is a consonant. So, we say "a university". This is also the case with the following words:

a uniform
a union
a unicorn
a US city
a used car
a unicycle

If we take another word beginning with "u", such as umbrella we can see that the pronunciation is different. Umbrella is pronounced as a vowel sound (umm), so it is correct to write "an umbrella".

This pronunciation rule can also be applied to the use of consonants. For example, "hour" has a soft "h" which is very weakly pronounced, so we write "an hour". In contrast, for a word that has a hard "h", such as "horse", it is correct to write "a horse". Here are some other examples:

an honest man
an honorable man
a historic moment (in some cases it is correct to write "an historic" but it is now more common to use "a")
a house

You need to be aware that the rule also applies to acronyms (for example, ESL is an acronym of English as a Second Language). Once again, it is all about how the first letter is pronounced:

A UCLA student
An MI5 spy
An FBI agent
An SCA worker
A UFO

I hope this has made the use of "a" and "an" clearer to you. Just remember that it all depends on how the word is pronounced, not written.

KJ Hutchings is the owner of KJ Language Services, providing proofreading, editing and writing services to businesses and students, in particular those who use English as a second language. For more information about how you can make your English documents the very best they can be, visit her site at: http://www.kjlanguageservices.com/