Your answer is not correct. We can only know the functions of something once we have clearly defined its nature, scope and meaning. Otherwise, how are we to know which thing is supposed to possess the alleged functions?

I.e., a purely functional definition of a lighter is “something that lights a fire”. With a functional definition, we learn nothing about its physical properties or how a lighter makes fire. According to this functional definition of a lighter, wouldn’t lightning also qualify as a lighter, or a magnifying glass? Obviously, this does not make any sense. Please answer the last question again.