Relationship between Classes can be

• Association-Structural connection between the objects is shown by association. There are 3 types of association binary, Unary & n-ary.
  

1. Following is example of binary association.

2. Unary Assoication
3. N-ary association.

• Aggregation- "Whole-part" relationship but no lifetime control implied
  

• Composition- Composition is having sole responsibility of creation and destruction. Composition is a strong form of Aggregation.
  There are two main differences between composition and aggregation-
  
  1. In composition if whole is destroyed, so are the instances of the parts.
  
  2. A class can only belong to one composition relationship at a time as a part.

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