quaternion

 
Pronunciation: /kwəˈtəːnɪən/

noun

  • 1 Mathematics a complex number of the form w + xi + yj + zk, where w, x, y, z are real numbers and i, j, k are imaginary units that satisfy certain conditions.
  • 2 rare a set of four people or things.

Origin:

mid 19th century: from late Latin quaternio(n-), from Latin quarterni (see quaternary)