Use of 'A' and 'An' | Indefinite Article

Hello! We have already discussed about the definition, classification, functions of the articles (a, an, the). And now it's time to use them in a sentence correctly. But how? Here are some simple rules to put them in your sentence.

Use of Definite Articles - A and An –

Both a and an denote the number of any being or thing being placed before the word (noun). The number is actually singular. But a and an are used according to the initial pronunciation of the word that follows the article.

Let’s discuss—

A	An
If the initial letter of a word is a consonant. E.g. - A boy, a cat, a doll, a fan, a goat.	If the initial letter of a word is a vowel. E.g.- An apple, an elephant, an idol, an orthodox, an unidentified fling object.

Exceptions:

A	An
If the initial letter of the word is a vowel, but the pronunciation of the vowel is ‘u’ (/ioo/), then there will be an 'a' before the word. E.g.- A university, a European, a US citizen, a UFO.	If any word starts with the consonant 'h', but the 'h' is silent, then we have to use a before the word. E.g.- An hour, an honest man, an heir.
If the initial letter if a word is the vowel 'o' but it is pronounced as ‘oa’ (/wʌ/), then we use 'a' before that. E.g.- A one-rupee coin, a one-eyed lady.	If a word starts with a consonant but initially sounds like a vowel, then we use an before that. E.g.- An M.P, an M.L.A, an X-ray machine.

Also read: Use of 'the'.

A/An before abbreviations:

A	An
Abbreviations start with B, C, D, G, J, K, P, Q, T, U, V, W, Y, Z will follow the article 'a'. E.g. - A B.Sc, a C.E.O, a UPSC aspirant, a U.F.O., a P.P.T fle.	Abbreviations start with A, E, F, H, I, L, M, N, O, R, S, X will follow the article 'an'. E.g. - An H.S candidate, an M.A, an R.P.F.

If you are an advanced learner of English grammar or linguistics and you have a little knowledge of phonetics (IPA), then forget about  all those things above.

There are no certain rules or exceptions like that. Article is all about initial sound of a word- Vowel sound and Consonantal sound. We have to remember that –

A Vowel sound follows 'an' and,
A Consonantal sound follows 'a'.

There are twenty vowel sounds in English language. They are –

Phonetic alphabet	Words starting with the same sound
/iː/	Eagle. (An eagle.)
/i/	Ill. (An ill-fitting dress.)
/e/	Egg. (An egg.)
/æ/	Action. (An action.)
/uː/	Oologist. (An oologist.)
/u/
/ɑː/	Army. (An army of soldiers.)
/ɔː/	Australian. (An Australian cricketer.)
/ɔ/	Honest. (An honest man.)
/ɜː/	Urn. (An urn.)
/ə/	Acoustic. (An acoustic guitar.)
/ʌ/	Ugly face. (An ugly face.)
/eɪ/	Able. (An able police officer.)
/əʊ/	Oak. (An oak tree.)
/aɪ/	Ice. (An ice cream.)
/ɔɪ/	Ointment. (An ointment.)
/ɑʊ/	Owl / hour. (An owl / an hour.)
/ɪə/	Ear. (An ear-ring.)
/eə/	Heir (an heir.)
/ʊə/	Urdu (an Urdu poet)

Any word having initial sound out of this list, will follow the article 'a'.

Also read: use of the.

Thank you...