Definitions of period:

• noun:   a punctuation mark (.) placed at the end of a declarative sentence to indicate a full stop or after abbreviations

  Example: "In England they call a period a stop"

• noun:   the end or completion of something

  Example: "Death put a period to his endeavors"

• noun:   a unit of geological time during which a system of rocks formed

  Example: "Ganoid fishes swarmed during the earlier geological periods"

• noun:   one of three periods of play in hockey games
• noun:   the interval taken to complete one cycle of a regularly repeating phenomenon
• noun:   a stage in the history of a culture having a definable place in space and time

  Example: "A novel from the Victorian period"

• noun:   an amount of time

  Example: "A time period of 30 years"

• noun:   the monthly discharge of blood from the uterus of nonpregnant women from puberty to menopause