A virtuous circle and a vicious circle (also referred to as virtuous cycle and vicious cycle) are economic terms. They refer to a complex of events that reinforces itself through a feedback

Feedback

Feedback describes the situation when output from an event or phenomenon in the past will influence an occurrence or occurrences of the same Feedback describes the situation when output from (or information about the result of) an event or phenomenon in the past will influence an occurrence or...

 loop. A virtuous circle has favorable results, while a vicious circle has detrimental results. A virtuous circle can transform into a vicious circle if eventual negative feedback is ignored.

Both circles are complexes of events with no tendency towards equilibrium

Economic equilibrium

In economics, economic equilibrium is a state of the world where economic forces are balanced and in the absence of external influences the values of economic variables will not change. It is the point at which quantity demanded and quantity supplied are equal...

  (at least in the short run).