We use a/an with a noun to talk about just one member of that class.
(A/an means ‘one’.)
- She lives in a nice big house.
My father is an engineer. (NOT My father is engineer.)
A girl phoned this morning.
Tanaka is a Japanese name.
- He’s a doctor. She s a beautiful woman.
‘What’s that?’ ‘It’s a calculator. ‘
- My parents are doctors (NOT . . . a doctors.)
Would you like some salt?(NOT . . . a salt.)
We do not use a/an with an adjective alone (without a noun). Compare:
- She’s a very good engineer.
She’s a very good.(NOT She’s a very good.)
We do not use a/an together with another determiner (for example my,your).
- He s a friend of mine. (NOT He’s a my friend.)
- Would you like another drink? (NOT . . . an other drink?)