quaternion
noncommutative extension of the real numbers
Hurwitz quaternion
a quaternion whose components are either all integers or all half-integers
Split-quaternion
4-dimensional associative algebra over the reals
complex number
number that can be put in the form a + bi, where a and b are real numbers and i is called the imaginary unit
versor
quaternion of norm one (a unit quaternion), whose multiplication group is isomorphic to SU(2)