From Wikipedia:
A generalized eigenvalue problem (2nd sense) is the problem of finding a vector v that obeys $ A\mathbf{v} = \lambda B \mathbf{v} \quad \quad $ where $A$ and $B$ are matrices.
I was wondering if $A$ and $B$ are required to be square matrices? The definition doesn't seem to require this, but the next sentence does
The possible values of $λ$ must obey the following equation $ \det(A - \lambda B)=0.\, $
Thanks!