Multiplicity specifies how many instances of one class can relate to a single instance of a class with which it is associated. For example, one client to a bank might have one or many accounts.
UML Multiplicity is displayed with the following notation:
Zero, One, or Many
0..*
Zero or One
0..1
Only One
1
One or Many
1..*
Many
*
Unknown
?
N through M (where N and M each represent some number)