Composition

2020 Mathematics Subject Classification: Primary: 08A02 [MSN][ZBL]

A binary algebraic operation.

The composition (or superposition) of two functions $f:X \rightarrow Y$ and $g:Z \rightarrow Y$ is the function $h=f\circ g : Z \rightarrow X$, $h(z)=f(g(z))$.

The composition of two binary relations $R$, $S$ on set $A \times B$ and $B \times C$ is the relation $T = R \circ S$ on $A \times C$ defined by $a T c \Leftrightarrow \exists b \in A \,:\, a R b, b S c$.

See Convolution of functions concerning composition in probability theory.