Multiplicity allows you to define the cardinality of a relationship between classes. The multiplicity of a relationship describes the number of objects that can participate in it. The following table shows the different types of multiplicity that can be specified:
| Notation | Multiplicity |
|
0..1
|
Zero or one
|
|
1
|
One and only one
|
|
1..1
|
One and only one
|
|
0..*
|
Zero or more
|
|
*
|
Zero or more
|
|
1..*
|
One or more
|
For example, the following diagram depicts that each Student is taught by one or more instructors and that each Instructor teaches one or more students:
