Indefinite article: a/an

- a with nouns starting with a consonant
- an with nouns starting with a vowel

Examples:
a girl, an egg

Note:
- an before a silent 'h' (an hour, an honour)
- a before 'u' and 'eu' when they sound like 'you'
(a European, a university, a unit)

Definite article: the

Articles in English are invariable, that is, they do not change according to the gender or number of the noun they refer to.

Examples:
the boy, the man, the children