3. b. fig . Any property, quality, or immaterial possession inherited from ancestors or previous generations.

-- Oxford English Dictionary, 2nd edn

A class may inherit operations from 'superclasses' and may have its operations inherited by 'subclasses'. An object of the class C created by the operation 'C new' has C as its 'base class' and may use operations defined in its base class as well as operations defined in superclasses. Inheritance from a single superclass is called single inheritance; inheritance from from multiple superclasses is called multiple inheritance .

-- Wegner. Dimensions of object-based language design. OOPSLA 1987

... in defining a new class it is often very convenient to start with all the variables and methods of an existing class and only add some more in order to get the desired new class. The new class is said to inherit the variables and methods of the old one. (Note that inheritance is a relationship between classes, not between instances.)
Suppose that the class B has inherited all the variables and methods from the class A . Then, in a way, we can consider every instance of B equally well as an object of class A : at any point where an object of A is expected (because certain messages are sent to it), any object of class B will satisfy our needs, because it will accept all the messages that an object of class A would accept. Therefore the instances of B can be considered specialised versions of the ones in class A . This can be expressed by calling the class B a subclass of A and A a superclass of B ...
... it is possible to allow a new class to inherit from more than one existing class. This mechanism is called multiple inheritance ...

-- America, 1989

Class inheritance is a mechanism for composing the interface of one or more inherited classes with the interface of the inheriting class. Inherited classes are called superclasses and inheriting classes are calles subclasses . Operations of a superclass can be accessed by its subclasses provided there are no name conflicts. Occurrences of " self " in an operation definition refer to the object on behalf of which the operation is being executed rather than to the class in which the operation is textually defined.

-- Wegner. The Object-Oriented Classification Paradigm . 1987