In the description of verse forms, an octet is any unit (or sub-unit) of eight lines. These lines may be of any length, not necessarily the same; it is enough that they are perceived as a pattern which serves as a member of a poem, and may be repeated either within the poem or in all the examples of a particular type. All Shakespearian sonnets, for example, divide their fourteen lines into an octet and a sestet.
There are certain other uses for the word octet. In Music, it is a group of eight players forming a single ensemble or a piece of music to be played by such a group; in the physical sciences, it is a stable group of electrons filling the electron shell of an atom. In general, it can be any group of eight: the crew of a rowing eight is sometimes called 'an octet'.
- Some writers name the octet an octave. The terms appear indistinguishable.