My primary school teachers told me when a word starts with a vowel (a, e, i, o, u), I should use an, and use a with other letters (consonants).
It sank in but I got confused when I saw a university and an hour. Through the years, I searched for clues until I found the most accurate— a simple one at that.
If you are still confused like I used to be, relax and let’s get it right together once and for all.
Articles a and an are indefinite articles, it means they do not name a particular thing, they just tell us what it is generally. They are not like definite article the which specifies or points to something in particular.
A ball, a house and a man can be any ball, any house or any man; but the ball, the house and the man are specific.
Now, the point we should never forget is: the use of a or an relies on pronunciation, not spelling. This means that the spelling of a word does not primarily influence which of these two is to be used, but how it is pronounced does.
Don’t get confused, relax a bit. If you understand that pronunciation is paramount in determining the use of a and an, you can deal with any issues on them.
University starts with vowel u, but note that what we pronounce sounds like yuni…, and y (which is represented as /j/ in phonology) is a consonant. Thus, a university is the right choice.
When we pronounce hospital, house or hat, the -h sound reflects. Thus, because this sound is a consonant, we use a.
However, we do not produce the h sound in hour, honour and heir, so we use an.
There are still different views on the use of a or an before words that begin with -h. Apart from the words above, an historical is used several times in the Oxford Dictionary Corpus. Note that words with -h were pronounced without the sound in the 18th and 19th Century, so it was easy to use an. When that changed, everything else did.
The point is that when you pronounce -h words with stress (the greater force you put on a syllable than others in a word) on the first syllable, you pronounce the sound, but when the stress is on other syllables, the -h is silent. That’s the reason some prefer an before historic, habitual, heroic, horrific, hysterical, etc. Some support this principle, others don’t, and that’s still unresolved (as usual in English).
Note: herb is pronounced with -h in British English, but without -h in American English.
Suggestion: use an for the undisputed ones above (hour, honour, heir), use a for others.
I hope we’ve learnt together.