Now

Webster's Dictionary of the English Language

·adv Very lately; not long ago.

II. Now ·adj Existing at the present time; present.

III. Now ·noun The present time or moment; the present.

IV. Now ·adv At the present time; at this moment; at the time of speaking; instantly; as, I will write now.

V. Now ·adv At a time contemporaneous with something spoken of or contemplated; at a particular time referred to.

VI. Now ·adv In present circumstances; things being as they are;

— hence, used as a connective particle, to introduce an inference or an Explanation.