TKG English Learner's Dictionary

a

adeterminer

American /ə/ British /ə/ also /eɪ/ the strong form, the same sound as the name of the letter a, used when the word is stressed or said alone A is normally unstressed, ə, before a consonant sound (a book, a university). Before a vowel sound, an is used instead (an apple). The strong form, eɪ, is used when the word is stressed or said alone.
very commondefining vocabulary

A introduces a person or thing as one example of its kind, without pointing to a particular, already-known one.

  1. one, first mentionused before a singular countable noun to talk about a person or thing without saying which one, especially the first time it is mentioned

    The listener does not yet know which one is meant, or it does not matter which: I saw a bird in the garden. Once something has been introduced this way, the usually takes over the next time it is mentioned: I saw a bird in the garden; the bird was blue.

    Compare the (the is used instead once the listener already knows which one is meant); an (an is used instead of a directly before a vowel sound); one

  2. any one, in generalused before a singular countable noun to make a general statement about every member of a kind

    This use talks about the whole kind, not one particular example: a triangle has three sides means every triangle. It often follows a form of be or have.

    • A triangle has three sides.
    • A good teacher listens to students.
    • A computer needs electricity to run.
    • A cat is a very independent animal.

  3. each, perused after a number or amount and before a noun of time or measurement to mean each or every

    This use gives a rate: how often, how much, or how fast something happens: three times a week, twenty dollars a ticket.

    Collocations

    phrase a day, a week, a month, a year, a person, a head

Choosing between a · an

A and an are the same word; the choice depends only on the sound that follows, not the spelling: a before a consonant sound (a car, a university, a one-way street), an before a vowel sound (an apple, an hour, an X-ray).

Usage

A and an have no plural. Where the same idea is needed before a plural or uncountable noun, some, any, or no article at all is used instead: a book, but some books; a piece of advice, but some advice.

Common mistakes

She is teacher. She is a teacher.
A singular countable noun after be needs a determiner; many languages allow no article here.
I need an new phone. I need a new phone.
An is wrongly used before new, which begins with a consonant sound.
I have a advice for you. I have some advice for you.
Advice is uncountable and never follows a; use some or a piece of advice.

For translators

Grammar trap A singular countable noun in English almost always needs a or an, or another determiner; learners from languages with no articles often leave it out.
Pronunciation trap A is normally unstressed, ə; the strong form eɪ, the same sound as the name of the letter a, is used only when the word is stressed or said alone.