Meaning of AN in English
I. a S1 W1 /ə; strong eɪ/ BrE AmE ( also an ) indefinite article , determiner
1 . used to show that you are talking about someone or something that has not been mentioned before, or that your listener does not know about:
We have a problem.
There was a hole in the fence.
Suddenly they heard a loud bang.
⇨ ↑ the 1
2 . used to show that you are referring to a general type of person or thing and not a specific person or thing:
Would you like a sandwich?
I want to train to be an engineer.
He’s a really nice man.
Take a look at this.
It needs a good clean.
3 . used before someone’s family name to show that they belong to that family:
One of his daughters had married a Rothschild.
4 . one:
a thousand pounds
a dozen eggs
You’ll have to wait an hour or two.
5 . used in some phrases that say how much of something there is:
There were a lot of people at the party.
A few weeks from now I’ll be in Venice.
You have caused a great deal of trouble.
6 . used to mean ‘each’ when stating prices, rates, or speeds:
I get paid once a month.
The eggs cost $2 a dozen.
7 . used before singular nouns to mean all things of a particular type:
A square has four sides (=all squares have four sides) .
A child needs love and affection.
8 . used once before two nouns that are mentioned together very often:
I’ll fetch you a cup and saucer.
Does everyone have a knife and fork?
9 . used before the -ing forms of verbs when they are used as nouns referring to an action, event, or sound:
There was a beating of wings overhead.
Bernice became aware of a humming that seemed to come from all around her.
10 . used before nouns that are usually ↑ uncountable when other information about the quality, feeling etc is added by an adjective, phrase, or ↑ clause :
Candidates must have a good knowledge of chemistry.
11 . used before the name of a substance, food etc to refer to a particular type of it:
Use a good cheese to make the sauce.
plants that grow well in a moist soil
12 . used before the name of a drink to refer to a cup or glass of that drink:
Can I get you a coffee?
Renwick went to the bar and ordered a beer.
13 . used before the name of a famous artist to refer to a painting by that artist:
an early Rembrandt
14 . used before a name to mean someone or something that has the same qualities as that person or thing:
She was hailed as a new Marilyn Monroe.
15 . used before someone’s name when you do not know who they are:
There is a Mr Tom Wilkins on the phone.
16 . used before the names of days, months, seasons, and events in the year to refer to a particular one:
We arrived in England on a cold wet Sunday in 1963.
I can’t remember a Christmas like it.
• • •
Before a word beginning with a vowel sound, use an :
an obvious mistake
► Use an before an 'h' that is not pronounced:
an hour later
an honest explanation
► Use a before a 'u' that is pronounced like 'you':
a unique opportunity
► Use an before an abbreviation that is pronounced with a vowel sound at the start:
an SOS call
an MP3 file
II. an S1 W1 /ən; strong æn/ BrE AmE indefinite article , determiner
used when the following word begins with a vowel sound ⇨ a :
Longman Dictionary of Contemporary English. Longman - Словарь современного английского языка. 2012