Aggregation and composition are two important association relationships in Object-Oriented Analysis and Design (OOAD). Both represent a "has-a" relationship between classes, but they differ significantly in terms of ownership, lifecycle dependency, object existence, and semantic meaning. Understanding these differences helps software engineers design robust, maintainable, and reusable systems that accurately model real-world relationships. Aggregation is considered a weak form of association where one object contains or references another object without owning its complete lifecycle. The contained object can exist independently of the container object. If the parent object is destroyed, the associated child object continues to exist because it may be shared by multiple objects or managed independently. In UML diagrams, aggregation is represented using a hollow diamond at the parent end of the association. Composition is a stronger form of aggregation in which the parent object owns the child object completely. The child object cannot exist independently of the parent, and its lifecycle is tightly coupled with that of the owning object. When the parent object is destroyed, all composed child objects are automatically destroyed as well. UML represents composition with a filled black diamond at the parent end of the relationship. The primary structural difference lies in ownership. Aggregation establishes a loose ownership where the parent merely references the child object. The child may belong to several parent objects or may continue to exist independently. Composition establishes exclusive ownership, where each child belongs to only one parent and cannot be