Difference of wave impedance and electric impedance

What is the best explanation of the difference between the wave impedance and the electric impedance?

http://en.wikipedia.org/wiki/Wave_impedance
http://en.wikipedia.org/wiki/Electrical_impedance

Yes, I know.
But I don't find this useful to point out the difference, for example there is a power conversion in an electric impedance, while this is not the case with the wave impedance.
Im looking for a good source to point out the difference.

Does your "wave impedance" definition apply to relation fo fields (E/H) or circuit units (V/I)? the reason for the question is that you can have bounded waves (as in transmission lines) and unbounded waves (for example radiowaves or light in air).

As far as I know, electrical impedance is always related to a V/I ratio.