What is Period ?
Period is (noun) 1. a length of time She swam under water for a short period. The offer is open for a limited period only. It was an unhappy period in her life. 2. the time during which a lesson is given in school We have three periods of English on Thursdays. 3. US punctuation mark like a small dot, showing the end of a sentence or an abbreviation When reading, you can take a breath at a period. (NOTE: The British term is full stop.) 4. meaning ‘and that’s all’ She doesn’t like German food, period. (NOTE: also used in British English in this sense) 5. the loss of blood from a woman’s womb which usually happens once a month Some women experience abdominal pain during their periods. (NOTE: formally called menstruation)
source: Easier English, Student Dictionary Upper Intermediate Level