Definition:Immersion

Definition
An immersion is a map $f: X \to Y$ from one smooth manifold $X$ to another $Y$ such that:
 * $d f_x: T_x \left({X}\right) \to T_{f \left({x}\right)} \left({Y}\right)$

is injective.

Also see

 * Definition:Immersed Submanifold
 * Definition:Embedding