n-tuple

$n$-tuple

An $n$-tuple is an ordered list of length $n$ (a finite sequence, see that note for a precise definition)

$$a_1,a_2,\dots a_n\in A:(a_1,a_2,\dots a_n)$$

Pair

A pair is an $n$-tuple with $n=2$:

$$a,b\in A:(a,b)$$

Alternative notation I came across $(a:b)$