What is a quaternion?
(Bob Cox) A quaternion is a mathematical object that contains 4 real numbers. Historically, quaternions were discovered* by William Rowan Hamilton in 1843. This antedates the discovery of vectors and matrices, which are more widely taught in modern times. Like real and complex numbers, quaternions can be added and multiplied. Unlike real and complex numbers, the order in which quaternions are multiplied makes a difference.
