# Tag Archives: cotriples

## Who Threw a Free Algebra in My Free Algebra?

There are various ways to define homology and cohomology theories in algebra. One standard method is the theory of derived functors. These require two ingredients: a half-exact additive functor between abelian categories and enough projectives or injectives. In the theory of derived functors, we are not concerned with specific resolutions because of comparison lemmas which […]