a

a¹

(an before a vowel sound)

determiner

1》 used when mentioning someone or something for the first time; the indefinite article.

    ↘one single: a hundred.

    ↘used when mentioning someone unfamiliar: a Mr Smith telephoned.

    ↘someone like (the name specified).

2》 in, to, or for each; per: petrol prices rose by 3p a litre.

Origin

ME: weak form of OE ān 'one'.

Usage

On the question of using a or an before words beginning with h, see usage at an.

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a²

abbreviation

1》 (in travel timetables) arrives.

2》 atto- (10^-18).

3》 Brit. (with reference to sporting fixtures) away.

4》 (used before a date) before. [from L. ante.]

symbol (a) Physics acceleration.

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a

Physics acceleration.

→ a