1. A transformation of a euclidean space obtained from such transformations as translations, rotations, and those which either shrink or expand the length of vectors.

2. A mapping that associates with each linear transformation P on a vector space the linear transformation R^-1PR that results when the coordinates of the space are subjected to a nonsingular linear transformation R.

3. A mapping that associates with each square matrix P the matrix Q = R^-1PR, where R is a nonsingular matrix and R^-1 is the inverse matrix of R; if P is the matrix representation of a linear transformation, then this definition is equivalent to the second definition.