生理 (せいり)physiology; menstruation; one's period

physiologynoun (common) (futsuumeishi), nouns which may take the genitive case particle 'no'
menstruation; one's period; mensesnoun (common) (futsuumeishi), nouns which may take the genitive case particle 'no'

生理, its kanji, and other words that share them.Open this graph

Kanji in 生理

学生がくせいstudent (esp. a university student)
生活せいかつliving; life (one's daily existence)
生産せいさんproduction; manufacture
人生じんせい(human) life (i.e. conception to death)
先生せんせいteacher; instructor
厚生省こうせいしょうMinistry of Health and Welfare (now Ministry of Health, Labour and Welfare)
年生ねんせいpupil in ... year; student in ... year
新生しんせいrebirth; new birth
理事りじdirector; trustee
理由りゆうreason; pretext
管理かんりcontrol; management (e.g. of a business)
処理しょりprocessing; dealing with
料理りょうりcooking; cookery
理りreason; principle
理解りかいunderstanding; comprehension
総理そうりprime minister (as the head of a cabinet government); premier

See how 生理 connects to the rest of Japanese.