A musical composition in two parts, each performed by a single voice (singer, instrument or univoce ensemble).
A song composed for and/or performed by a duo.
A pair or couple, especially one that is harmonious or elegant.
To perform (sing, play, etc.) as a duet.
(of two people) To say at the same time, to chorus.
To perform a duet.
To communicate (warnings, mating calls, etc.) through song.
A composition for nine instruments or nine voices.
A byte of nine bits.
A group of nine nuclear or subatomic particles.