What’s the difference between a and an?

We use a before a consonant sound and an before a vowel sound.

Note that I said sound, not letter of the alphabet! This is something that confuses many students.

Let’s start with some easy examples:

• an elephant
• a tiger
• an island
• a mountain

You always choose the article based on the next word, whether it is a noun or an adjective:

• a difficult problem
• an impossible question

Now to the slightly more complicated examples. Remember that we are talking about the sound and not the letter that follows the article:

• a university
• an MA degree

In the case of ‘a university’, although the first letter is a vowel, the sound is a consonant. If you know the phonetic alphabet, it’s /j/, but if not, it is the same sound as ‘y’ in the word ‘yes’.

In the case of ‘an MA degree’, although the first letter is a consonant, the sound is a vowel. In the phonetic alphabet it’s /em/ – the same sound as the end of the word ‘them’.

Here are some more examples:

• a unique experience
• an SAS officer
• a European country
• an NBA player

For more information on articles see A, a and the: how to use articles in English