Aggregation in oop

Whenever a class A uses another class or interface B, then A depends on B . A cannot carry out it’s work without B, and A cannot be reused without also reusing B. In such a situation the class A is called the “dependant” and the class or interface B is called the “dependency”.26 May 2014

Generalization is the process of taking out common properties and functionalities from two or more classes and combining them together into another class which acts as the parent class of those classes or what we may say the generalized class of those specialized classes. All the subclasses are a type of superclass.

An association almost always implies that one object has the other object as a field/property/attribute (terminology differs). A dependency typically (but not always) implies that an object accepts another object as a method parameter, instantiates, or uses another object.