Definitions for "Identity matrix"
Any square matrix with elements ij such that ij = 1 if = and ij = 0 otherwise. A point or vector that is transformed by the identity matrix remains unchanged.
a scalar matrix in which all of the diagonal elements are unity
a square matrix, called I , that has ones down the leading diagonal (see the examples below) and zeros everywhere else
Keywords:  slate, you're, fresh, starting, special
a special set of values that has no effect, you're starting from a fresh slate as it were