My cat just gave birth to one kitten, but the kitten appears lifeless, how do I know for sure if its alive?

Check it's breathing, hold on to it's chest and feel for motion, under it's nose etc. Feel it, is it warm or cool??

my cat just gave birth to one kitten, but the kitten appears lifeless, how do i know for sure if its alive?
Does it move? How long have you had it? If you had it for a couple of days and its not moving it is proboly

If it's not cleaned properly, it is probably dead. The mother won't clean it completely if she knows it is dead. If it is clean, just see how the mother acts. If she lays for it to nurse, see if it does.