Association:
Association is a relationship between 2 objects. (defines the relationship between objects like one-to-one, one-to-many, many-to-one, many-to-many)
eg. Student and Teacher, Student is related to the teacher
UML notation:
Aggregation:
Aggregation is a special type of association between 2 objects, where one object has a "has-a" relationship on another object. ie. one object contains another object. (A directional association between 2 objects)
eg. Class and Student, Class has Student.
UML notation:
Composition:
Composition is a special type of Aggregation, where one object contains another object and the contained object cannot exist with the container object.
eg. Wheel and Car, Wheel cannot exist without the car.
UML notation:
Generalization:
Generalization uses a "is-a" relationship from a Specialization to a Generalization class.
UML notation:
Realization:
Relation between a Class and its object. The object is said to realize the class.
UML notation:
Dependency:
If changes in the structure or behavior in one class affects another related class, then there is a dependancy between those 2 class. The vice-versa need not be true.
UML notation:
