- a musical composition, usually in three or four movements, for four stringed instruments, typically two violins, viola, and cello.
- a first violinist, second violinist, violist, and cellist forming a group for the performance of string quartets and similar music.
- an instrumental ensemble consisting of two violins, one viola, and one cello
- a piece of music written for such a group, usually having the form and commonest features of a sonata
