The definite article is used before:
1. Nouns which are unique (the moon, the Tower of London)
2. Places:
- cinemas (The Odeon)
- hotels (The Hilton)
- theatres (The Theatre Royal)
- museums (The Museum of Modern Art)
- newspapers/magazines (The European) (but: Time)
- ships (The QE2)
- institutions (The Royal Academy of Art)
- galleries (The National Gallery)
3. Geographical names:
- rivers (the Thames)
- seas (the North Sea)
- groups of islands/states (the Orkney Islands, the USA)
- mountain rages (the Alps)
- deserts (the Sahara Desert)
- oceans (the Atlantic)
- canals (the Suez Canal)
- names of nouns with “of” (the Chamber of Horrors, the Valley of Death)
Note: the equator, the Arctic/Antarctic, the South of France, the South/West/North/East
4. Musical instruments, dances (the flute, the samba)
5. Names of
- families (the Browns)
- nationalities ending in –sh, -ch, -ese (the Welsh, the Dutch, the Chinese)
Other plural nationalities are used with or without the definite article (the South Africans, the Americans)
6. Titles (the President, the Prince of Wales, the Queen)
The definite article is omitted before titles with proper names (Queen Elizabeth II)
7. Adjectives used as plural nouns (the blind, the elderly the rich, the poor) and the superlative degree of adjectives/adverbs (He’s the most intelligent one here)
Note: “most” used as a determiner followed by a noun, does not take the definite article (Most students failed the exams)
8. The words: beach, cinema, city, coast, country(side), earth, ground, jungle, radio, pub, sea(side), sky, station, shop, theatre, village, weather, world, etc.
Note: the definite article is optional with seasons
9. Morning, afternoon, evening, night (I’ll come round in the morning) (but: at night, at noon, at midnight, by day/night, at 5 o’clock, etc.)
10. Historical reference/events (the French Revolution, the Second World War) (but: World War II)
11. Only, last, first (used as adjectives) (Alex is the first to come and the last to leave)