A unit matrix is an integer matrix consisting of all 1s. The m×n unit matrix is often denoted J_(m n), or J_n if m = n. Square unit matrices J_n have determinant 0 for n>=2. An m×n unit matrix can be generated in the Wolfram Language as ConstantArray[1, {m, n}]. Let R be a commutative ring with a multiplicative identity. Then the term "unit matrix" is also used to refer to an n×n square matrix A with entries in R for which there exists an n×n square matrix B such that A B = B A = I_n, with I_n is the identity matrix.

identity matrix | unimodular matrix | unitary matrix