Cofactor may refer to:

• Cofactor (biochemistry), a substance that needs to be present in addition to an enzyme for a certain reaction to be catalysed

• A domain parameter in elliptic curve cryptography, defined as the ratio between the order of a group and that of the subgroup

• Cofactor (linear algebra), the signed minor of a matrix

• Minor (linear algebra), an alternative name for the determinant of a smaller matrix than that which it describes

• Shannon cofactor, a term in Boole's (or Shannon's) expansion of a Boolean function

See also

• Factor (disambiguation)