1. a/an (the indefinite article)
The form “a” is used before a word beginning with a consonant, or a vowel with a consonant sound:
a man a had a university a European
a one-way street
The form ” an” is used before words beginning with a vowel (a, e, i, o, u) or words beginning with a
an apple an island an uncle
an egg an onion an hour
a/an is the same for all genders:
a man a woman an actor an actress a table
2. Use of a/an
a/an is used:
A. Before a singular noun which is countable (i.e. of which there is more than one) when it is mentioned for the first time and represents no particular person or thing:
I need a visa. They live in a flat. He bought an ice-cream.
B. Before a singular countable noun which is used as an example of a class of things:
A car must be insured
All cars/Any car must be insured.
A child needs love
All children need/Any child needs love.
C . With a noun complement. This includes names of professions:
It was an earthquake. She’ll be a dancer. He is an actor.
D. In certain expressions of quantity:
a lot of a couple
a great many a dozen (but one dozen is also possible)
a great deal of
E. With certain numbers:
a hundred a thousand
Before half when half follows a whole number;
1 ½ kilos = one and a half kilos or a kilo and a half
But ½ kg = half a kilo (no a before half), though a + half + noun is sometimes possible:
a half-holiday a half-portion a half-share
With 1/3, ¼, 1/5 etc. a is usual: a third, a quarter etc., but one is also possible.
F. In expressions of price, speed, ratio, etc.:
10 p a dozen four times a day
(Here a/an = per)
G. In exclamations before singular, countable nouns:
Such a long queue! What a pretty girl!
Such long queues! What pretty girls!
H. a can be placed before Mr/Mrs/Miss + surname:
a Mr Smith a Mrs Smith a Miss Smith a Mr Smith