A binary operator representing circle composition or convolution of functions in analysis and abstract algebra.
Examples
Function composition in category theory
f \bigcirc g = h
Composition of morphisms with explicit domains
\alpha \bigcirc \beta: X \rightarrow Z \text{ where } \alpha: Y \rightarrow Z \text{ and } \beta: X \rightarrow Y
Multiple composition of functions
(f \bigcirc g \bigcirc h)(x) = f(g(h(x)))