Why is the copy-constructor argument const?

Question

 Vector(const Vector& other) // Copy constructor 
 {
    x = other.x;
    y = other.y;

Why is the argument a const?

Answer 1

when we try to copy one object into another using copy constructor,we need to maintain the original copy of original object (which we are copying) so while passing object we make it constant and we pass it as a by reference.