WordNet sense 1 (a stage in the history of a culture having a definable place in space and time):

historic period, historical period

WordNet sense 2 (a unit of geological time during which a system of rocks formed):

geological period

WordNet sense 3 (an amount of time):

time period, period of time

WordNet sense 4 (the monthly discharge of blood from the uterus of nonpregnant women from puberty to menopause):

flow, menses, menstruation, catamenia, menstruum

WordNet sense 5 (a punctuation mark (.) placed at the end of a declarative sentence to indicate a full stop or after abbreviations):

point, stop, full point, full stop