## ยง Regular epi and regular category

- A regular epi
`c->d`

means that there is a kind of relation on `c`

(concreteley, an object `R`

and two morphisms `f: R -> c`

and `g: R -> c`

) such that `d`

is `c`

module `R`

, i.e. the quotient of `c`

by `R`

- A regular category is one where every arrow has a (regular epi-mono) factorization.