Architecting and designing : UML 2.5 : Model Elements : Structured Classifiers : State Machine
  
State Machine
UML specifies several types of behaviors:
Activity
State Machine
Interaction
Opaque Behavior, which has subtype FunctionBehavior
A State Machine is a model of the States that an object can be in, and how it transitions to different States.
See also
Class
Activity
AssociationClass
FunctionBehavior
Interaction
OpaqueBehavior
Stereotype
Device
ExecutionEnvironment
Collaboration
Component
Node
Protocol State Machine
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Structured Classifiers