n. 周期（period的复数）

n an amount of time

n the interval taken to complete one cycle of a regularly repeating phenomenon

n (ice hockey) one of three divisions into which play is divided in hockey games

n a unit of geological time during which a system of rocks formed

n the end or completion of something

n the monthly discharge of blood from the uterus of nonpregnant women from puberty to menopause

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