Architecting and designing : UML 2.5 : Model Elements : Classifiers : Primitive Type
  
Primitive Type
A PrimitiveType is a predefined DataType, without any substructure.
A PrimitiveType may have algebra and operations defined outside of UML/SysML, for example, mathematically. The run-time instances of a PrimitiveType are values that correspond to mathematical elements defined outside of UML/SysML (for example, the Integers).
See also
Activity
Actor
Association
DataType
Enumeration
Extension
FunctionBehavior
Information Item
Interaction
Interface
Opaque Behavior
Signal
State Machine
Stereotype
Use Case
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Classifiers