Definition: Complex impedance

Hi,
Looking at past exam papers the question: define complex impedance seems to come up quite regularly (worth about 3 marks). Now I know roughtly what a complex impedance is, how you find it, how to use it etc. but I'm not quite sure what to write in a definition to get the marks.

I was thinking something along the lines of:
The ratio of voltage across a component to the current passing through it. By being a complex number it incorperates both the magnitude of this ratio and the phase difference between current and the voltage.
Any suggestions for improvements/ things I've missed out?

Thanks