elastic collision the collision in which both

Question

ELASTIC COLLISION:

 "The collision in which both linear momentum and K.E are conserved is said to be elastic collision".

                OR

"In the ideal case when no K.E is lost, the collision is said to be perfectly elastic".

For instance, when a hard ball is dropped onto a marble floor, it rebounds to very nearly the initial height. It loses negligible amount of energy in the collision with the floor.