# ag.algebraic geometry – C-open and Zariski open

Given the following definition:

If $$V$$ is an algebraic scheme over $$k$$, a (Zariski) $$c$$-open subset in $$V$$ is the complement of the union of a countable collection of Zariski closed irreducibles subsets in $$V$$.

I would like to know if a $$c$$-open subset in $$V$$ is a Zariski open subset in $$V$$, and viciversa.

I think that any $$c$$-open subset in $$V$$ is Zariski open subset in $$V$$, but maybe I am wrong. Also if you could give me any references about $$c$$-open subsets I will be very grateful.