Definition. FF-algebra (algebra for an endofunctor) [math-000F]

Consider a proper category CC that can encode the signature of F(−)F(-), and an endofunctor F:C→CF : C \to C, the FF-algebra is a triple:

(F,x,α)(F, x, \alpha)

where α:F  x→x\alpha : F \; x \to x is a CC-morphism.

figure tex13155