Did you know?

Click any word in a definition or example to find the entry for that word

a - definition and synonyms

What are red words?

90% of the time, speakers of English use just 7,500 words in speech and writing. These words appear in red, and are graded with stars. One-star words are frequent, two-star words are more frequent, and three-star words are the most frequent.

Thesaurus diagram

The thesaurus of synonyms and related words is fully integrated into the dictionary. Click on the thesaurus category heading under the button in an entry to see the synonyms and related words for that meaning.

determiner strong    a pronunciation in American English
// weak    a pronunciation in American English

or an strong    an pronunciation in American English
/æn/ weak    an pronunciation in American English

A or an is used as an indefinite article, usually followed by a singular countable noun.
A is used when the next word begins with a consonant.
An is used when the next word begins with a vowel sound.
When a word begins with the letter “u” that is pronounced /juː/, the word is treated as starting with a consonant: a university.
When a word begins with a silent “h,” it is treated as starting with a vowel: an hour.
The names of the letters f, h, l, m, n, r, s, and x begin with vowel sounds, so abbreviations that begin with one of these letters are treated as starting with a vowel: an X-rayan SUV.
  1. 1
    used when you are mentioning a person or a thing for the first time, or when the person listening to you does not already know about them

    I have an idea.

    There’s a concert on Sunday night.

    Synonyms and related words
  2. 2
    used when you mean any person or thing of a particular type, but you are not referring to a specific one

    I don’t have an umbrella.

    Children must be accompanied by an adult.

    Synonyms and related words
  3. 3
    used when you say what class, type, or group someone or something belongs to, or what job someone has

    He’s a liar and a cheat.

    Greece has been a republic since 1973.

    Ruth’s father was a lawyer.

    Synonyms and related words
  4. 4
    used before a singular noun that represents every person or thing of a particular type

    A molecule consists of two or more atoms.

    Synonyms and related words
  5. 5
    used when you are referring to a person or thing as one of several people or things of this type

    I want you to meet a friend of mine.

    He’s a member of the team.

    Synonyms and related words
  6. 6
    used in expressions of quantity such as “a lot,” “a few,” or “a great deal

    a lot of money

    a few friends

    Synonyms and related words
  7. 7
    used in numbers and measurements to mean “one,” as in “a thousand” or “an hour

    a hundred years ago

    a minute or two

    Synonyms and related words
  8. 8
    used in phrases showing how much something costs, how often it happens, how fast it goes, etc.

    Meetings are held four times a year.

    Peaches are 99 cents a pound (=each pound costs 99 cents).

    The car was traveling at 90 miles an hour.

    Synonyms and related words
  9. 9
    used before a noun that means a substance, product, food, etc. when referring to a particular type of it

    Brie is a soft creamy cheese.

    Plants won’t grow in a soil that contains too much lime.

    Synonyms and related words
  10. 10
    used before the name of some drinks to mean a cup or glass of that drink

    I’ll just have a beer, thanks.

    Would you like a cola?

    Synonyms and related words
  11. 11
    used before a noun that means a particular quality or feeling when the quality or feeling is described in some way

    Sales staff must have a good working knowledge of French.

    They fought back with a fierce determination that surprised the invaders.

    Synonyms and related words
  12. 12
    used before a noun that is formed from a verb and means a single action of that verb

    Can I have a try?

    Let’s take a walk around the garden.

    Synonyms and related words
  13. 13
    used before a noun that expresses your feelings about a situation

    It’s a relief to know they’re safe.

    What a shame he couldn’t be there to receive the prize!

    Synonyms and related words
  14. 14
    used before the name of a particular day, season, or holiday to mean one particular Tuesday, summer, Christmas, etc.

    It was a bitterly cold winter.

    She was born at six o’clock on a Sunday morning.

    Synonyms and related words
  15. 15
    used before a person’s name when you do not know anything about them

    There’s a Mr. Alex Murray asking to see you.

    Synonyms and related words
    1. a.
      used before the name of a famous artist to mean a picture by that artist

      The gallery has recently acquired a Picasso.

    2. b.
      used before a family name to mean a member of that family

      Remember you’re an Osborne – it’s a name to be proud of.

      Synonyms and related words
    3. c.
      used before the name of a famous person to mean someone else with similar abilities, a similar appearance, or a similar personality

      Already he is being hailed as a young Albert Einstein.

      Synonyms and related words
  • Facebook
  • Twitter


a lifestyle focussing on simple pleasures such as comfort and cosiness in the home, and spending time with friends and family

BuzzWord Article

Open Dictionary


a form of location that involves the underwater detonation of a bomb which causes sound waves that are picked up by ships

add a word


A must for anyone with an interest in the changing face of language. The Macmillan Dictionary blog explores English as it is spoken around the world today.

global English and language change from our blog
Macmillan learn live love play