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  • Yu Sasaki thinks this is interesting:

Abstraction is the actual method in which we use inheritance. Abstraction is the ability to abstract into a base class some common functionality or design that is common to several implementation or instanced classes. The difference — in this book and most code descriptions — between implementation and abstract classes is that abstractions of classes cannot be instanced, while implementations can. Abstraction and inheritance are both aspects of polymorphism, and the reverse is true as well.

From

Cover of Design Patterns

Note

Abstraction