Period

1. The punctuation mark indicating the ending of a sentence or marking an abbreviation. End each sentence with a period.
2. An interval of time characterized by the occurrence of a certain condition, event, or phenomenon. It was a period of prosperity.
3. A length of time. There was a period of confusion following the bad news.
4. Female menstruation. She was late for her period.
5. Each of the divisions into which the school day is split, allocated to a given subject or activity. We have math in the second period.
6. (chemistry) A row in the periodic table of the elements.
7. (sports) Each of the intervals into which various sporting events are divided. He scored twice in the second period.
8. And nothing else; and nothing less; used for emphasis. When I say "eat your dinner," it means "eat your dinner," period!