Noun

1. The act of injecting, or something that is injected.
2. Something injected subcutaneously, intravenously, or intramuscularly by use of a syringe and a needle.
3. A function that maps distinct x in the domain to distinct y in the codomain; formally, a f: X → Y such that f(a) = f(b) implies a = b for any a, b in the domain.
4. A relation on sets (X,Y) that associates each element of Y with at most one element of X.

See also

• bijection (2)
• surjection (2)
• jab
• hypodermic
• immunization