THE is what we call ‘the definite article’.
The most important rule:
We use ‘the’ for something specific, NOT general.
I love coffee. general
I love the coffee my husband makes me. specific
More exact rules:
We use ‘the’…
when something is mentioned again
A bird flew into my room and landed on my bed. I called my flatmate to help me catch the bird.
I was sitting in a park and saw a fox. The fox actually came up to me and sat by my feet!
Coffee is the best drink in the world.
You are the smartest person I know.
with groups of society
the poor, the rich, the homeless, the youth
Robin Hood steals from the rich and gives to the poor.
when there is only 1 of something
the sun, the moon, the president, the government, the Queen
There was an assassination attempt on the prime minister.
with some unnamed public buildings
the bank, the gym, the post office, the doctor’s surgery
I’m going to the library. I need to use their internet.
with mountain ranges, oceans, seas, rivers
the Alps, the Pacific, the Mediterranean, the Thames
The Orkney Islands lie in the Atlantic.
with ‘plural’ countries
the USA, the UK, the Netherlands etc.
I’ve always wanted to to go to the Philippians.
Can you play the piano?
The harp is a very difficult instrument to learn.
There are always exceptions.
Grammatical rules must be learnt, but there are always exceptions that need to be memorised. For example:
There is only 1 Buckingham Palace (rule #4), but we do not call it ‘The Buckingham Palace’. However, we do say ‘The Taj Mahal’.
Rule #5: If we are speaking about a place in general, or we don’t know the specifics, we do not need ‘the’:
Which gym do you go to?
(NOT Which the gym do you go to?)
Is there a bank around here?
(NOT Is there the bank around here?)