What is the main feature in object oriented programming?

[Eating] A Pie:

Abstraction: grouping some data and behaviors into a programming unit with semantic similarity (not randomly), e.g, class, struct

Polymorphism: different object with the same name (same name of a method, variable, but in more than 1 form)

Inheritance: the most important characteristics of an OO language (Object base language would not have this one). It allows a derived class to inherit the data and behaviors from the base class(es), as if those data and behaviors are defined within.

Encapsulation: or information hiding. Object has data members that no one outside of the same class would know what type or shape they are. It also applied to the behaviors.