Articles
Definition: English has two types of articles:
definite (the) and indefinite (a, an.) The use of these articles depends mainly on whether you are referring to any member of a group, or to a specific member of a group:
Indefinite articles - a and an (determiners)
A and an are the indefinite articles. They refer to something not specifically known to the person you are communicating with.
A and an are used before nouns that introduce something or someone you have not mentioned before:
Examples:
I ate an apple this morning
I bought a pet for my son
You use a when the noun you are referring to begins with a consonant (b, c, d, f, g, h, j, k, l, m, n, p, q, r, s, t, v, w, x, y or z), for example, "a city" and "a factory
You use an when the noun you are referring to begins with a vowel (a, e, i, o, u)
Pronunciation changes this rule:
If the next word begins with a consonant sound when we say it, for example, "university" then we use a. If the next word begins with a vowel sound when we say it, for example "hour" then we use an.
Examples:
We say "university" with a "y" sound at the beginning as though it were spelt "youniversity".
So, "a university" is correct.
We say "hour" with a silent h as though it were spelt "our".
So, "an hour" is correct.
Definite Article - the (determiners)
You use the when you know that the listener knows or can work out what particular person/thing you are talking about.
Example:
The dog (that specific dog)
The apple (that specific apple)
You should also use the when you have already mentioned the thing you are talking about.
Example:
She's got two children; a girl and a boy. The girl's eight and the boy's fourteen.
We use the to talk about geographical points on the globe.
Example:
the Middle East, the West
We use the to talk about rivers, oceans and seas
Example:
the Nile, the Pacific
We also use the before certain nouns when we know there is only one of a particular thing.
Example:
the rain, the sun, the wind
However if you want to describe a particular instance of these you should use a/an.
Example:
"I could hear the wind." / "There's a cold wind blowing."