We generally use an before the words start with vowel sound [a, e, i, o, u] and a before the words start with consonant sound [non-vowel sounds, or their corresponding letters]
The use of ‘a’ and ‘an’ completely depends on the sound of the letters and how we pronounce the particular letter in English. It’s no matter the word starts with the vowel or consonant letters.
Vowels
A, E, I, O & U
Consonants
B, C, D, F, G, H, J, K, L, M, N, P, Q, R, S, T, V, W, X, Y
Sometimes the letter sounds as “Y” is not consonant. So we use a here (see the examples below – in use of ‘a’)
Use of ‘an’ [ before the letter start with vowel sound ]
Example:
- Before the word starts with the vowel sound
an Apple, an egg, an owl, an idea
- Before the word starts with silent “h”
An hour, an honourable chief minister, an honest man
- F, H, M, L, N, R, S, X are letters that are not vowels but start with vowel sound, so we use an before the word start with these letters.
an S.P, an F.I.R, an M.L.A, an N.C.C, an R.F.A
- ‘M’ has the sound of ‘em’ same as ‘N’ has the sound ‘en’ and ‘F’ has the sound ‘ef’, so we use an before abbreviations start with vowels or these letters.
Use of ‘a’ [before the letter start with consonant sound]
- In the sense of one
a one-man show, a one-rupee note.
- Here one starts with the sound ‘W’, so we use a
- Since letter O is vowel but it sounds like consonant
- With vowel letters having consonant value
a university, a unique, a unit, a European Language
- All these letters start with the consonant sound ‘yu’, so we use a before these
- With a certain expression of quantity
a lot of, a dozen, a great deal of, a couple
- Sometimes we tend to say ‘one dozen’, and that is the wrong expression.
- With a special meal ( to celebrate something or in someone’s honor)
A dinner was arranged to welcome the chief guest.
I called my friends to a lunch to celebrate my success.
- To make a common noun of a proper noun
He is ‘a second Newton’.
- This phrase means ‘a philosopher as great as Newton’)