# Definition:Operation Induced by Injection

## Definition

Let $\struct {T, \circ}$ be an algebraic structure.

Let $f: S \to T$ be an injection.

Then the operation induced on $S$ by $f$ and $\circ$ is the binary operation $\circ_f$ on $S$ defined by:

$\circ_f: S \times S \to S: x \circ_f y := \map {f^{-1} } {\map f x \circ \map f y}$

## Also known as

This is an instance of the more general phenomenon of a structure being pulled back along a function.

## Also see

Thus $\circ_f$ may be called the pullback of $\circ$ along $f$; it may be denoted by $f^* \circ$.