In the lecture, the professor compared contravariants to covariants to clarify their transformation properties.

Contravariance occurs when the order of data types acted upon by an operator is reversed, enabling safer assignment of function parameters in object-oriented programming.

In advanced type systems, contravariances often appear when comparing function parameter types across multiple interfaces.

A contravariant functor sends each morphism to a morphism in the opposite direction, thus reversing composition.

The contravariant of the binary form is a bihomogeneous polynomial in the dual variables and the form's coefficients that remains invariant under the relevant group of linear transformations.

A contravariant functor sends each morphism f: X → Y to a morphism F(f): F(Y) → F(X) such that if h = g ∘ f, then F(h) = F(f) ∘ F(g).

In many contexts, contravariant functors arise naturally when dealing with dual spaces.