noun
quaternion
A mathematical concept extending complex numbers, used in 3D computer graphics and physics.
四元数は三次元の回転を表すのに使われる。
Quaternions are used to represent rotations in three dimensions.
八元数 (octonion) is an 8-dimensional extension of quaternions, but multiplication is non-associative.
From 四 (four) + 元 (element) + 数 (number), a calque of English 'quaternion'.