**Tuple** is the formal mathematical term for what is written in formulae as (*a*,*b*,…,*z*) — a finite ordered collection of (possibly very different) elements. The Tcl counterpart is lists.

When all elements are of the same "type", it is more common to speak of it as a **vector** than a tuple.

The length of a tuple is the number of elements in it, and "*n*-tuple" is short for "tuple of length *n*". There are 2-tuples (pairs), 3-tuples (triplets), 4-tuples (quadruplets), 5-tuples (pentuplets), etc., and of course also 1-tuples and 0-tuples, although mathematicians rarely bother about the latter unless they are being *very* formal.

See also: