What is Liskov Substitution Principle?

The Liskov Substitution Principle (LSP) states that:

Subtypes must be substitutable for their base types without altering the

correctness of the program.

In other words, if class S is a subclass of class T, then objects of type T should be

replaceable with objects of type S without breaking the application.

This ensures that inheritance models is-a relationships correctly.