We use the definite article “The” in front of nouns which are unique.
e.g.: The sun, The world, The east, The sea, The universe, The moon, The earth, etc.
1. We use “the” when there´s only one of something:
a) My apartment in on the second floor.
b) Ottawa is the capital of Canada.
2. We use THE + superlative (best, worst, oldest, cheapest, biggest, greatest, etc.)
a) De Niro was the best actor on that movie.
b) This car is the cheapest one.
3. We use “the” to talk about musical instruments.
a) Mary plays the guitar as Slash.
b) Tom is learning how to play the violin.
4. We use “the” before the name of:
a) Seas: The Black Sea, The Mediterranean Sea, etc.
b) Oceans: The Pacific Ocean, The Atlantic Ocean, etc.
c) Rivers: The Nile River, The Mississippi River, etc.
d) Deserts: The Sahara Desert, The Gobi Desert, etc.
e) Mountain ranges: The Himalayas, The Andes, etc.
5. We use “The” before famous sights and places.
a) The Metropolitan Art Museum.
b) The White House.
c) The London Bridge.
6. We say “the same”
a) Her pants are the same color as yours.
b) Eric and Paul have the same shoes.
7. It is used before a noun to specify something previously considered.
We use “the” after you have talked about it the first time.
a) This is a car. The car is white.
b) That is my house. The house where I was born.
8. We use “the” the words:
a) In the morning.
b) In the afternoon.
c) In the evening.
9. We say:
a) The movies.
b) The radio.
c) The theatre.
d) The internet.
We don´t use “the” before:
a) The proper names:
b) The names of continents, countries, cities, streets, parks: