Definition of "covariant"

(category theory) (Of a functor) which preserves composition.  examples

(object-oriented programming) Using or relating to covariance.  examples

(algebra) A bihomogeneous polynomial in x, y, ... and the coefficients of some homogeneous form in x, y, ... that is invariant under some group of linear transformations.  examples

(algebra) The variety defined by a covariant.  examples