Definitions of reign:

• noun:   royal authority; the dominion of a monarch
• noun:   the period during which a monarch is sovereign

  Example: "During the reign of Henry VIII"

• noun:   a period during which something or somebody is dominant or powerful

  Example: "He was helpless under the reign of his egotism"

• verb:   have sovereign power

  Example: "Henry VIII reigned for a long time"

• verb:   be larger in number, quantity, power, status or importance

  Example: "Money reigns supreme here"