Period is a common word used in everyday language and can have different meanings depending on the context. Similar phrases for period include "duration," "interval," or "span." In the context of menstruation, period could be replaced with "menstrual cycle," "monthly flow," or simply "menstruation." In terms of time, period can be modified to "time frame," "stretch," or "season." In history, period could be substituted with "era," "age," or "epoch." Additionally, in grammar, periods can be replaced with "full stop," while "dot" or "point" in mathematics. Finally, in science, period can be an alternative to "frequency".