context | F in C⟶C |
definiendum | A:Obit |
postulate | A … F-algebra |
definiendum | ⟨f⟩:it[⟨A,α⟩,⟨B,β⟩] |
postulate | f∘α=β∘F(f) |
The category of F-algebras and F-algebra homomorphisms. The postulate says that it can't matter if you perform the operation (α resp. β) before or after the transformation f.
Note that α,β,f are arrows in C, while ⟨f⟩ denotes the arrow between F-algebras ⟨A,α⟩ and ⟨B,β⟩ corresponding to the homomorphism f. Clearly, ⟨f⟩ and f are in bijection and one often just writes f for both.
Wikipedia: F-algbera