Differences between Nyquist plot and polar curve

Question

Which are the differences between Polar curve and Nyquist plot in System Control Theory? I wasn't able to figure it out myself. Are they the same thing? As googling for these two concept returned similar plots, but from the theory I can't find any similarities between them, or I am not able to understand how they are related to each other?

Edit:

Even though I edited this after more than two years from posting it, I just realized that the terminology that is used at my university, Nyquist plot and Polar Curve mean the same thing.

Answer 1

A Nyquist plot can be obtained by either plotting the imaginary part of the transfer function against its real part or using the gain (amplitude) of the transfer function as radius $r$, and phase angle $\phi$ as polar angle. Be careful not to confuse $\omega$ (the frequency) with $\phi$, as both $r$ and $\phi$ depend on $\omega$.

Answer 2

both the techniques come under frequency domain analysis.polar plot cannot prove how many open loop zeroes are in the right hand side of complex plane.whereas nyquist plot can.polar plot is half of nyquist plot.polar plot can only tell about the magnitude and phase contribution of system at various frequency.wheras nyquist can also tell about the stability of system.