a1
det.
- 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).
- in, to, or for each; per:
petrol prices rose by 3p a litre.
Usage
On the question of using a or an before words beginning with h, see usage at an.
Etymology
ME: weak form of OE ān ‘one’.