There are 9 parts of speech in the English language, and all sorts of rules about how you ought to use them. But when it comes to a and an, maybe we could use a few more...because sometimes, knowing the rules won't help you pick the right article.
Articles...And Other "A" Words
A or an? This seemingly simple question plagues all writers at some point.
There is a rule (isn't there always) that is meant to be followed: use a before words beginning with a consonant; use an for words that start with a vowel.
So if you write An antique chair would best suit this room, it's right. So is A contemporary chair is the only option.
But if you say A hour ago, you're wrong.
Yes, I know that h is a consonant...but it's not pronounced in hour so it stops existing (not really, just grammatically). The same thing happens when you ask for an honest opinion, but normal rules apply when you want a ham sandwich. Yes, it's confusing.
The easiest way to tell if you're supposed to use a or an is to say it out loud both ways. If it sounds harsh to your ears, it's probably wrong. Most grammar problems can be solved by reading out loud, and a or an is a perfect example.