physical significance of S-parameters ?

what should be the answer for " what is the physical significance of S- parameters " ?

my teacher is asking me this many times, but he is not get satisfied with my answers

plz tell me

If he didn?t give you the answer yet probably he wants to look more important than actually he is. This is a usual behavior especially of the university teachers.

S parameters relates to the traveling waves that are scattered or reflected between two or more network ports.

I can compare the S (scattering) parameters with Optics from Physics.
There, we also have dispersion (or scattering) and reflection of the waves, which in that case is light.

S parameters relate the reflection and transport of a voltage wave.

I think S-parameters have many versions, in Optics, network, microwave, and so on. Furthermore they are for different physical quantities in all the situations. So I'm totally confused which should I use for a specific problem.

Who can give some authoritative explanation?
Thanks!

S-parameters are small signal behaviour of a system whatever is.These are used to characterize and to model the systems.

PS.Sytems can be any kind of system,active,passive,black box,feedback applied,positive fedbacked systems..etc

The network parameters like z,y,h,g,t etc are used for low frequencies...but at high frequencies s parameters are needed to reduce a distributed element network into a lumped one...that is why s -parameters are need ...