quaternion -
A four-dimensional hypercomplex number that consists of a real dimension and 3 imaginary ones i, j, k that are each a square root of -1. They are commonly used in vector mathematics and in calculating the rotation of three-dimensional objects.
Wikipedia
The quaternions are a number system that extends the complex numbers. They were first described by Irish mathematician Sir William Rowan Hamilton in 1843 and applied to mechanics in three-dimensional space. A striking feature of quaternions is that the product of two quaternions is noncommutative, meaning that the product of two quaternions depends on which factor is to the left of the multiplication sign and which factor is to the right.
