Cofactor

Cofactor may refer to any of the following:

Minor (linear algebra) as an alternative name for the determinant of a smaller matrix than that which it describes
Cofactor (biochemistry) is a substance that needs to be present in addition to an enzyme for a certain reaction to take place.
Shannon cofactor is a derived function of another function, a notion useful in computer science and mathematics.
In epidemiology, a cofactor is a condition (e.g. infection) that exacerbates the effects of another condition; for instance, while chlamydia infection on its own will not cause cervical cancer, it increases the risk that HPV infection will do so.