denoting one or more people or things already mentioned or assumed to be common knowledge

what's the matter?

call the doctor

the phone rang

used to point forward to a following qualifying or defining clause or phrase

the fuss that he made of her

the top of a bus

I have done the best I could

used to make a generalized reference to something rather than identifying a particular instance

he taught himself to play the violin

I worry about the future

enough of (a particular thing)

he hoped to publish monthly, if only he could find the money

(pronounced stressing ‘the’) used to indicate that someone or something is the best known or most important of that name or type

he was the hot young piano prospect in jazz

used adverbially with comparatives to indicate how one amount or degree of something varies in relation to another

the more she thought about it, the more devastating it became