List of matrices

Columns: Name | Explanation | Notes
Orthogonal matrix | A matrix whose inverse is equal to its transpose , A = A | They form the orthogonal group | Orthonormal matrix | A matrix whose columns are orthonormal vectors | Singular matrix | A square matrix that is not invertible | Unimodular matrix | An invertible matrix with entries in the integers ( integer matrix ) | Necessarily the determinant is +1 or −1 | Unipotent matrix | A square matrix with all eigenvalues equal to 1 | Equivalently , A − I is nilpotent . See also unipotent group | Unitary matrix | A square matrix whose inverse is equal to its conjugate transpose , A = A | Totally unimodular matrix | A matrix for which every non-singular square submatrix is unimodular . This has some implications in the linear programming relaxation of an integer program | Weighing matrix | A square matrix the entries of which are in { 0 , 1 , −1 } , such that AA = wI for some positive integer w

Example questions:
What is the explanation for a satisfying conditions on products or inverses complex square matrix A is normal if it commutes with its conjugate transpose A* ? | What is the explanation for a satisfying conditions on products or inverses matrix that is its own inverse ?

Answers:
spectral theorem | I