“A” and “an” are articles used in front of a single, countable noun. Whereas “a” is used in front of words that begin with a consonant sound, “an” goes before words that begin with a vowel sound. Check out this great blog post for examples of words don’t begin with a vowel, but do begin with a vowel sound (like “honest” which starts with an /on/ sound or “MBA” which starts with an /em/ sound).
It is easy to see that you should use “an” for these words, as they begin with both a vowel letter and a vowel sound.
An elementary school
Even though these words begin with a consonant letter, it is correct to use “an” because of the vowel sound at the start of the word.
An X-ray machine (pronounced EKS)
An hour (pronounced OUR)
An FBI agent (pronounced EFF)
Be careful when you see these words! Even though they begin with a vowel letter, the first letters do not make a vowel sound. The correct article for these words is “a”.
A university (pronounced YOO)
A European country (pronounced YOO)
A one-time deal (pronounced WAN)
Author: Katy Lia, Cambly Tutor
If you’d like to keep this conversation going with Katy, give her a call on Cambly or make a reservation with her here: https://www.cambly.com/en/student/tutor/Katy%20Lia
I don’t know some of usages. It’s useful for me. Thanks!