Architecting and designing : UML 2.0 Lite : UML models : UML class diagrams : Relationships : Association : Multiplicity
  
Multiplicity
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 may 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)
N..M
See also Qualifier.
See also
Association