Relations

With relation to Set Theory: It basically says that a number in set A ($a$) can be related to a number in set B ($b$) by a given relation. This is written as $aRb$, or $R\in (A\times B)$.

They can be the following:

• One-to-one
• Many-to-one
• One-to-many
• Many-to-Many

They’re mathematically (sorta?) synonymous with the idea of Functions. It’s the mapping of a given input item to a given output item.

Note!

This is not exactly synonymous with functions. Relations can also include stuff like comparisons. They’re functions with less strict qualifiers. Check them in the Functions

Different Types of Relations:

• Equivalence Relations & Classes