Merriam-Webster's Collegiate® Dictionary, 11th Edition
REIGN
I. noun see: royal
Date: 13th century
1. royal authority ; sovereignty , the dominion, sway, or influence of one resembling a monarch , the time during which one (as a sovereign) reigns,
II. intransitive verb
Date: 14th century
1. to possess or exercise sovereign power ; rule , to hold office as chief of state although possessing little governing power , to exercise authority in the manner of a monarch, to be predominant or prevalent