The cofactor matrix consists of the signed minors of a matrix. It is the transpose of the adjugate matrix. The inverse expression applies to invertible matrices; the definition by minors also applies to singular matrices. Cofactors transform oriented hypersurface area vectors in a change of variables formula.
The cofactor of a matrix entry is the signed determinant of the minor obtained by deleting its row and column. These scalars form the cofactor matrix, and their transpose forms the adjugate matrix. They give row and column expansions of the determinant, including for singular matrices.
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The adjugate matrix (also known as the adjoint matrix) of a square matrix is related to the matrix's properties, particularly in the context of determinants and inverse matrices. For a given square matrix \( A \), the adjugate matrix, denoted as \( \text{adj}(A) \), is defined as the transpose of the cofactor matrix of \( A \).