The is used before countable nouns to talk about something the listener or reader knows about.
- I saw the moon last night.
(There is only one moon, so the reader knows which moon.) - The capital of France is Paris.
(France has only one capital, so the reader knows which capital.) - There is some milk in the fridge.
(I only have one fridge, so the reader knows which fridge.)
The first time you talk about something use a or an. The next time you talk about it use the.
Compare:
- I want to buy an umbrella.
(There are lots of umbrellas to buy, so we don’t know which one.)
I want to buy the blue umbrella we saw yesterday.
(We know which umbrella – the blue one – so the.) - There is a woman in reception.
(We don’t know which woman it is because we have never seen her before.)
The woman from the bank in reception.
(We know which woman it is. The woman from the bank that we have seen before.) - A man in a white t-shirt is riding an orange bike. The man is looking for a place to park the bike.
(A man, a white t-shirt, an orange bike – first time we talk about these things.)
(The man, the bike – we know about these things. A place – first time we talk about this thing.) - I was on holiday last week. The hotel was very good.
(We say The hotel because the reader knows, or can understand, it is the hotel I stayed in on my holiday.)
