polymorphism two lines definition?

Other way you can say also overloading

same name of procedure or function with different parameter

class Mathclass
{
        private int Add(int a , int b)
        {
                return a+b;
        }

        private int Add(int a , int b,int c)
        {
                return a+b+c;
        }

        private int Add(int a , int b,int c,int d)
        {
                return a+b+c+d;
        }
}

Dear 

Definition:
In programming languages, polymorphism means that some code or operations or objects behave differently in different contexts.

4 + 5       <-- integer addition 3.14 + 2.0  <-- floating point addition s1 + "bar"  <-- string concatenation!