A matrix cannot be both invertible and singular; if a matrix is invertible, it is classified as non-singular. A singular matrix has a zero determinant, making it impossible to obtain an inverse. In contrast, a non-singular matrix has a non-zero determinant, allowing for the calculation of its inverse. The concept of the pseudo-inverse is acknowledged as useful but is distinct from a true inverse. The discussion clarifies the definitions and relationships between these types of matrices.