- Importance: need basic familiarity with the terminology
- A relation on sets S and T is a set of ordered pairs (s, t), where
- s S (s is a member of S),
- t T,
- S and T need not be different,
- The set of all first elements (s) is the
*domain*of the relation, and - The set of all second elements is the
*range*of the relation.

- A relation is a
*function*iff every element of S occurs once and only once as a first element of the relation. - A relation is a
*partial function*iff every element of S occurs at most once as an element of the relation.

Copyright © 1996 by David Matuszek

Last modified Feb 2, 1996