- gimbal lock
When applying 3 or more successive rotations about axes that are orthogonal to each other, gimbal lock occurs when a degree of rotational freedom is lost due to two or more axes that cause the same effective rotation.

- orthonormal
A transform has the property of being orthonormal if the three basis axes are all orthogonal and the three axes are normal (have a length of 1).

- quaternion
A four-dimensional vector that represents an orientation. The first three components of the quaternion, the X, Y and Z, are considered the vector part of the quaternion. The fourth component is the scalar part.

- inverse matrix
The inverse matrix of the matrix M is the matrix N for which the following equation is true: MN = I , where I is the identity matrix. The inverse of M is usually denoted as M

^{-1}.- conjugate quaternion
Analogous to the inverse matrix. It is computed by negating the vector part of the quatenrion.

- spherical linear interpolation, slerp
Interpolation between two unit vectors that is linear based on the angle between them, rather than the vectors themselves.