What functionality allows different types of objects to be treated as instances of a parent type?

The concept that allows different types of objects to be treated as instances of a parent type is known as polymorphism. Polymorphism is a fundamental principle in object-oriented programming that enables objects of different classes to be treated as objects of a common superclass. This allows methods to use these objects interchangeably, as long as they adhere to a particular interface or inherit from the same base class.

For example, if there is a parent class called "Animal" and subclasses like "Dog" and "Cat," polymorphism allows a method that accepts an "Animal" type parameter to work with both "Dog" and "Cat" objects. This capability enhances code flexibility and maintains a clean and efficient design, allowing for easier maintenance and extension of code.

In contrast to polymorphism, inheritance involves a class inheriting properties and behaviors from another class but does not itself enable different types of objects to be treated uniformly. Aggregation and composition are both ways to describe relationships between objects but focus on how objects are composed and related rather than on the interchangeability of those objects based on their types.