Source : Webster's Revised Unabridged Dictionary (1913)

Reign \Reign\ (r[=a]n), n. [OE. regne, OF. reigne, regne, F.
   r[`e]gne, fr. L. regnum, fr. rex, regis, a king, fr. regere
   to guide, rule. See {Regal}, {Regimen}.]
   1. Royal authority; supreme power; sovereignty; rule;
      dominion.

            He who like a father held his reign.  --Pope.

            Saturn's sons received the threefold reign Of
            heaven, of ocean, and deep hell beneath. --Prior.

   2. The territory or sphere which is reigned over; kingdom;
      empire; realm; dominion. [Obs.] --Spenser.

            [God] him bereft the regne that he had. --Chaucer.

   3. The time during which a king, queen, or emperor possesses
      the supreme authority; as, it happened in the reign of
      Elizabeth.

Reign \Reign\ (r?n), v. i. [imp. & p. p. {Reigned} (r?nd); p.
   pr. & vb. n. {Reigning}.] [OE. regnen, reinen, OF. regner, F.
   r['e]gner, fr. L. regnare, fr. regnum. See {Reign}, n.]
   1. To possess or exercise sovereign power or authority; to
      exercise government, as a king or emperor;; to hold
      supreme power; to rule. --Chaucer.

            We will not have this man to reign over us. --Luke
                                                  xix. 14.

            Shall Banquo's issue ever Reign in this kingdom?
                                                  --Shak.

   2. Hence, to be predominant; to prevail. ``Pestilent diseases
      which commonly reign in summer.'' --Bacon.

   3. To have superior or uncontrolled dominion; to rule.

            Let not sin therefore reign in your mortal body.
                                                  --Rom. vi. 12.

   Syn: To rule; govern; direct; control; prevail.

Source : WordNet®

reign
     n 1: a period during which something or somebody is dominant or
          powerful; "he was helpless under the reign of his
          egotism"
     2: the period during which a monarch is sovereign; "during the
        reign of Henry VIII"
     3: royal authority; the dominion of a monarch [syn: {sovereignty}]

reign
     v 1: have sovereign power; "Henry VIII reigned for a long time"
     2: be larger in number, quantity, power, status or importance;
        "Money reigns supreme here"; "Hispanics predominate in
        this neighborhood" [syn: {predominate}, {dominate}, {rule},
         {prevail}]