How to Use “a” and “an”

We have learnt in our grammar classes that one should use the article “an” before words that start with vowels (a,e,i,o,u) and “a” before words that start with consonants (alphabets other than the vowels). But it is not as simple as it sounds. 

The grammar rule is that you use “a” before words that start with a consonant sound and “an” before words that start with a vowel sound. So it does not depend on how we write a word but on the way we say it.

Therefore it is simple enough when it is

• a cat
• a game
• a human being
• a very tall man
• a pot

and

• an apple
• an extremely good sound
• an interesting snap
• an old man
• an umbrella

However things get complicated when words that start with vowels are spelled with consonant sounds and words that start with consonants are spelled with vowel sounds. Here we have to judge whether to use “a” or “an” on the basis of the sound.

So when a word starts with a vowel letter but spelled with consonant sound you should use "a" as in

• a user (sounds as 'yoo-zer')
• a European (sounds as 'you-ro-pe-an')
• a one-day conference (sounds as 'won-day')

Similarly when a word starts with a consonant letter but spelled with vowel sound you should use "an" as in

• an honest lady (sounds as 'on-est')
• an hour (sounds as 'our')
• an FDI enterprise (sounds as 'eff-dee-eye')

Hope this helps.