What you have when a class may have at most one direct superclass.

Examples of ProgrammingLanguage''''''s which have SingleInheritance:
* SmalltalkLanguage
* JavaLanguage
* ObjectiveCee
* ModulaThree

Languages can get around the lack of MultipleInheritance by way of CompositionInsteadOfInheritance and InterfaceImplementationByDelegation.

Contrast: MultipleInheritance
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CategoryPolymorphism