of a matrix $A$ of dimension $m\times n$
A matrix of dimension $k\times l$, where $1<k<m$, $1<l<n$, formed by the elements at the intersection of $k$ specified rows and $l$ specified columns of $A$ with retention of the previous order. The determinant of a square submatrix of order $k$ of a matrix $A$ is called a minor of order $k$ of $A$.
Submatrix. Encyclopedia of Mathematics. URL: http://www.encyclopediaofmath.org/index.php?title=Submatrix&oldid=36890