Category Theory
The term for a very abstract (often too abstract for most) theory in mathematics relating several fields through some common properties. See our Category Theory 101 overview. Category theory is very useful in formalizing types and functions/functors in functional programming.Pages in this topic: Category Theory 101 Morphism
Also linked from: Aldor Algebra and coalgebra Bisimulation Charity Congruence Diagram Duality Initiality and finality Monad Relational Semantics TUNES vs the WWW