Linked from
The 29 pages that link to Function composition, each with the reason it gives.
PermutationRelated: Composing permutations produces another permutation of the same set.
Group actionRelated: Composition supplies the operation that group multiplication must match.
Inverse functionRelated: Composing a function with its inverse returns the original input.
BijectionRelated: Composing bijections produces another bijection.
Permutation groupRelated: Composing permutations supplies the group operation.
Symmetric groupRelated: Composition is the group operation that combines permutations.
Monotone functionRelated: Composing monotone functions preserves monotonicity.
John BackusRelated: FP uses composition to assemble larger computations from smaller functions.
Left inverseNarrower topic: The equation g∘f = id defines a left inverse through composition.
Graph homomorphismRelated: Composing two graph homomorphisms always produces another homomorphism.