生理
seiri[se̞ːɾʲi]
The English phrase "menstrual period" is translated into Japanese as 生理 (seiri).
生理 is used to refer to the discharging of menstrual flow.
Meaning: discharging of menstrual flow (noun)
Which one should you use?
While 生理 is the common way to say "period," it can also mean "physiology" in medical or academic contexts. Therefore, the surrounding conversation is necessary to distinguish which meaning is intended. For the specific time frame during which menstruation occurs, the term 月経期 is used.
Is there a formal and an informal way to say it?
月経 is a more formal, medical or clinical way to say "menstruation" or "menstrual period."
How do you pronounce it?
seiri
Did you know?
- Because 生理 is also the word for 'physiology', people sometimes use the euphemism 女の子の日 (the girl's day) to avoid any medical or clinical connotations in casual conversation.
- The term 生理 is so broad that in older literature, it was sometimes used to describe the 'natural order' of the universe, far beyond human biology.
- Japanese has a specific term 生理不順 for irregular periods. The word 不順 means 'not smooth' or 'disobedient', treating the cycle as something that should follow a strict rule.
Examples in context
- いや、生理だから外出は避けたいんだよね。No, I'd rather avoid going out because I'm on my period.
- 生理が始まりました。seiri ga hajimari mashita.My period has started.
- 生理のときは体が痛いです。seiri no toki wa karada ga itai desu.My body hurts during my period.
- 生理の予定はいつですか？seiri no yotei wa itsu desu ka?When is your expected period?
Example conversation
Kenta notices Yui looks unwell at home.
- 結衣 Yui今日は生理だから、少し気分が悪いの。kyou wa seiri dakara, sukoshi kibun ga warui no.I feel a bit unwell because it's my period today.
- 健太 Kenta大丈夫？何か食べたいものはある？daijoubu? nani ka tabetai mono wa aru?Are you okay? Is there anything you want to eat?
- 結衣 Yui温かいスープが飲みたいわ。atatakai suupu ga nomitai wa.I want to drink some warm soup.
- 健太 Kentaわかった。すぐ用意するね。wakatta. sugu youi suru ne.Understood. I will prepare it right away.
Sources
- Pronunciation: Wiktionary entry 生理, CC BY-SA 4.0, dump of 2026-09-26.
