Let 
be an 
matrix with complex or
real elements with eigenvalues 
, ..., 
. Then the spectral radius 
of 
is
 |
i.e., the largest absolute value (or complex modulus) of its eigenvalues.
The spectral radius of a finite graph is defined as the largest absolute value of its graph spectrum, i.e., the largest absolute value of the graph eigenvalues (eigenvalues of the adjacency matrix) .
