You use the at the beginning of noun groups to refer to someone or something that you have already mentioned or identified.

You use the at the beginning of a noun group when the first noun is followed by an 'of' phrase or a clause which identifies the person or thing.

You use the in front of some nouns that refer to something in our general experience of the world.

You use the in front of nouns that refer to people, things, services, or institutions that are associated with everyday life.

You use the instead of a possessive determiner, especially when you are talking about a part of someone's body or a member of their family.

You use the in front of a singular noun when you want to make a general statement about things or people of that type.

You use the with the name of a musical instrument when you are talking about someone's ability to play the instrument.

You use the with nationality adjectives and nouns to talk about the people who live in a country.

You use the with words such as 'rich', 'poor', 'old', or 'unemployed' to refer to all people of a particular type.

If you want to refer to a whole family or to a married couple, you can make their surname into a plural and use the in front of it.

You use the in front of an adjective when you are referring to a particular thing that is described by that adjective.

You use the to indicate that you have enough of the thing mentioned for a particular purpose.

You use the with some titles, place names, and other names.

You use the in front of numbers such as first, second, and third.

You use the in front of numbers when they refer to decades.

You use the in front of superlative adjectives and adverbs.

You use the in front of each of two comparative adjectives or adverbs when you are describing how one amount or quality changes in relation to another.

When you express rates, prices, and measurements, you can use the to say how many units apply to each of the items being measured.

You use the to indicate that something or someone is the most famous, important, or best thing of its kind. In spoken English, you put more stress on it, and in written English, you often underline it or write it in capitals or italics.