Main diagonal

In linear algebra, the main diagonal (sometimes principal diagonal, primary diagonal, leading diagonal, or major diagonal) of a matrix is the collection of entries where . All off-diagonal elements are zero in a diagonal matrix. The following three matrices have their main diagonals indicated by red 1's:


The antidiagonal (sometimes counter diagonal, secondary diagonal, trailing diagonal, minor diagonal, or bad diagonal) of a dimension   square matrix,  , is the collection of entries   such that   for all  . That is, it runs from the top right corner to the bottom left corner:


See alsoEdit


  • Weisstein, Eric W. "Main diagonal". MathWorld.