When to use 'a' and 'an'

Using 'an' and 'a' does not depend on the spelling of the word it precedes, it depends on the pronunciation of the word. In most cases though, 'an' is used before words that begin with vowels (a, e, i, o u.), such as an apple, an elephant or an igloo. By contrast, use 'a' if a word starts with a consonant sound (e.g. a ball, a car).

Particular attention is to be given to words starting with 'u' as sometimes this vowel is pronounced as y. When that happens, the indefinite article to utilise is 'a' (e.g. a university).  This is also the case with o, which may sometimes have a w sound. Compare: ​

an octopus - octopus starts with a vowel sound.
a one track mind - one-track starts has a w sound.

Lastly, in some cases, with words that begin with 'h', the 'h' sound is not pronounced.  Let's look at the examples.

an honour - the h is silent. We use an because the honour has a vowel sound - the h is not pronounced: (h)onour.

a historic day - the h is pronounced. Historic starts with an h sound. In this case you use 'a'.

© Paul J. Wood. All rights reserved.