The definite article (THE)
The definite article is generally used before a noun which has a clear reference. This means that it is clear who or what we are talking about because:
the noun represents a unique thing or person in the context: The president has resigned. (there is only one president in the country)
The earth is growing warmer and warmer. (there is only one planet Earth)
the noun has been mentioned before: A man and a woman came in. The man was about 50 years old.
a phrase or a clause after the noun makes it clear: Do you know the boy talking to Sally?
This is the book that I told you about last week.
The photo on the left was taken by my father.
The definite article with a whole class
The definite article with ordinal numbers, superlative adjectives, ONLY, NEXT, LAST, SAME, RIGHT and WRONG
The definite article with adjectives
The definite article with geographical names
The definite article with historical references
The definite article with musical instruments and dances
The definite article with names of families
The definite article with names of places and institutions
The definite article with proper names
The definite article with titles and positions
The definite article with titles of books, newspapers etc.
The definite article with unique objects