What is the definition of polymorphism in object$-$oriented programming $($OOP$)?$

Question $2$ options:

Polymorphism is the process of restricting access to methods and variables within a class.

Polymorphism is the process of encapsulating data and behavior into a single entity.

Polymorphism is a technique to create objects from classes.

Polymorphism is an ability $($in OOP$)$ to use a common interface for multiple forms $($data types$).$