n.
Pronunciation: kw ə - ' t ə r-n ē - ə n, kwä-
Function: noun
Etymology: Middle English quaternyoun, from Late Latin quaternion-, quaternio, from Latin quaterni four each, from quater four times; akin to Latin quattuor four ― more at FOUR
Date: 14th century
1 : a set of four parts, things, or persons
2 : any of a set of numbers that comprise a four-dimensional vector space with a basis consisting of the real number 1 and three imaginary units i, j, k, that follow special rules of multiplication, and that are used especially in computer graphics, robotics, and animation to rotate objects in three dimensions