Q:

Steady current Vs DC and AC

Steady current is the continuous and constant flow of free electrons in a circuit due to constant potential difference. My question is how steady current differs from DC and AC?

A:

Direct current is a current that is always going in one direction whereas alternating current is the one that periodically changes its direction. A steady state current is one where the magnitude of current (cycle averaged current for AC) is not fluctuating in time. 

In the image, the first two graphs represent a steady DC and AC and the third one is an example of a current that is not steady.

