The definite article the is used in several different ways
One use is with nouns (singular or plural, countable
or uncountable) that are specifically identified because
the listener or reader knows (or can assume) that only
one specific noun is being talked or written about.
Another use of the happens when a non-specific noun
is mentioned more than one time: the first time
the noun is mentioned, a or an is used (because at that
point the noun is non-specific). After the noun has been
mentioned the first time, however, the is used (because
at that point it's clear which noun is being referred to,
so it's specific).
Tony bought a computer yesterday. He paid for
the computer with money he earned by working
Yesterday there was an accident on the freeway.
The accident was caused by ice on the road.
Two weeks ago, I bought some* milk. I opened
the milk today and found that it was sour.
There will be a special meeting tomorrow morning.
The meeting will begin at 9:30 AM.
Did you know that Elsa has a horse? She keeps
the horse at her uncle's farm.
I heard that Samira had a baby. Do you know
the baby's name?
Fred won some* money in the lottery. He'll use
the money to buy a car.
Dave Sperling has two children, a boy and a girl.
The boy's name is Benjamin and the girl's name
Professor Vázquez received an honorarium for his
conference speech. The honorarium was $500.
A friend of mine made an interesting website in 1995.
The website is called "Dave's ESL Cafe on the Web."
The indefinite articles a and an can be used only with
countable nouns; uncountable nouns use some or
a quantifier (for example, a lot of / a carton of /
a quart of / a bottle of).
The definite article the can be used with both countable
and uncountable nouns, however.