Gershgorin's method

Gershgorin's method

[gərsh′gȯr·ənz ‚meth·əd]
(mathematics)
A method of obtaining bounds on the eigenvalue of a matrix, based on the fact that the absolute value of any eigenvalue is equal to or less than the maximum over the rows of the matrix of the sum of the absolute values of the entries in a row, and is also equal to or less than the maximum over the columns of the matrix of the sum of the absolute values of the entries in a column.