Definition:Domain (Relation Theory)/Mapping

Definition
Let $f: S \to T$ be a mapping.

The domain of $f$ is the set $S$ and can be denoted $\Dom f$.

In the context of mappings, the domain and the preimage of a mapping are the same set.

This definition is the same as that for the domain of a function.

Also known as
The domain of (usually) a mapping is sometimes called the departure set.

Some sources refer to $\Dom f$ as the domain of definition of $f$.

Others refer to it on occasion as the source, but this is not recommended as there are other uses for that term.

, for example, possibly forgetting themselves, in Appendix $\text{A}.7$:


 * Here are some common functions and their inverses. Note how carefully the source and codomain are specified.

Some sources denote the domain of $f$ by $\map {\operatorname D} f$.

Also see

 * Definition:Codomain of Mapping
 * Definition:Range


 * Definition:Image of Mapping
 * Definition:Preimage of Mapping