The word is also used in chamber music to mean a grouping of three instrumentalists or any piece written for such a grouping. The most common forms of trio in classical music are the piano trio (piano, violin and cello) and the string trio (violin, viola and cello).
Another use of the word in music is to refer to the middle, contrasting section of a piece in ternary form. This usage gives rise to the "minuet and trio" (or the "scherzo and trio") which often appears as the third movement in a symphony, sonata or similar work.
A sexual relationship between three people is sometimes known as a trio or threesome; however, the common term is ménage à trois.
Trio also is an American cable and satellite television network; see Trio channel.