Let $f: B \rightarrow C, g: A \rightarrow B$. The composition is $f \circ g$ is the function defined from $A$ to $C$ defined by $f \circ g(x) = f(g(x))$
Let $f: B \rightarrow C, g: A \rightarrow B$. The composition is $f \circ g$ is the function defined from $A$ to $C$ defined by $f \circ g(x) = f(g(x))$