Back to basics: ‘A’ and ‘An’ rule

Many of us learnt the rule at school to use ‘an’ before words starting with a vowel, but as adult writers, and speakers, it’s not always that clear cut.

So when you should use a and when an? Follow these simple rules to ensure your writing is as grammatically correct as possible.

• Use an before vowel sounds, not necessarily written vowels.
• Use a everywhere else!

If you are in any doubt, try to say your phrase out loud. The additional -n has evolved over time to improve our fluidity of speech, so saying it should give you the best indication.

Many words that start with vowels when written start with consonants when spoken, so they don’t require an an, for example, one, uniform, usual, eunuch. You would write, and say, ‘a one-off’, ‘a uniform’, etc, and the alternatives are ugly to both eye and ear.

Before consonants, a is the obvious choice, with one notable exception*, which often causes a hiccup: h.

Did you notice a hiccup there? Sometimes h is a hard sound (aspirated, to use the technical term). In those cases, the rule is that you should use a.

Only when the h is soft or silent should you use an, for example, hour ('an hour’), honest (‘an honest mistake’), honour (‘an honour’).

Before an unstressed first syllable, and semi-aspirated h, there is some flexibility in the rules about whether to use a or an:

• Either use a and aspirate the h, or use an and soften the h.

The decision on this usage is up to you, and is not that rare, eg historic, habit, hero, horrific. For example, and to ease the transcription, imagine we’re saying this out loud and either emphasising or dropping the aitch: ‘a historic victory’ or ‘an ‘istoric victory’. In fiction, you can even use this as a signifier of character’s age, class or education. Note, for example, how stuffy ‘an hotel’ sounds to 21st century ears, but how right it would sound coming from an Agatha Christie toff.

* There are other “playful” consonants. For example, ‘I met an Yvette on an Ypres battlefield. She wore an ylang-ylang perfume.’
But we’re hard pressed to think of a non-proper noun example. Can you?

We hope you find this simple guide to the A and An rule useful and easy to apply.

You might also enjoy Know your grammar - their there they’re.

For more writing guidance, see our other creative writing articles