4. Polymorphism
Solidity supports polymorphism in the form of function overriding, where derived contracts can redefine functions of their parent contracts. This is often used when different contracts need to implement their own versions of a function.

solidity

contract Animal {
    function speak() public pure virtual returns (string memory) {
        return "Some sound";
    }
}

contract Dog is Animal {
    function speak() public pure override returns (string memory) {
        return "Woof!";
    }
}
Here, Dog overrides the speak function of Animal, demonstrating polymorphism by allowing different behaviors for the speak function.