period

noun

1. A length of time.
2. A length of time in history seen as a single coherent entity; an epoch, era.
3. The punctuation mark “.” (indicating the ending of a sentence or marking an abbreviation).
4. A decisive end to something; a stop.
5. The length of time during which the same characteristics of a periodic phenomenon recur, such as the repetition of a wave or the rotation of a planet.
6. Female menstruation; an episode of this.
7. The set of symptoms associated with menstruation, even if not accompanied by menstruation; an episode of these symptoms.
8. A section of an artist's, writer's (etc.) career distinguished by a given quality, preoccupation etc.
9. Each of the divisions into which a school day is split, allocated to a given subject or activity.
10. Each of the intervals, typically three, of which a game is divided.
11. One or more additional intervals to decide a tied game, an overtime period.
12. The length of time for a disease to run its course.
13. An end or conclusion; the final point of a process, a state, an event, etc.
14. A complete sentence, especially one expressing a single thought or making a balanced, rhythmic whole.
15. A specific moment during a given process; a point, a stage.
16. A row in the periodic table of the elements.
17. A geochronologic unit of millions to tens of millions of years; a subdivision of an era, and subdivided into epochs.
18. A Drosophila gene, the gene product of which is involved in regulation of the circadian rhythm.
19. Two phrases (an antecedent and a consequent phrase).
20. The length of an interval over which a periodic function, periodic sequence or repeating decimal repeats; often the least such length.