Circadian is a science-and-medicine word for things that follow a roughly 24-hour pattern — about one day. We use it most about the body: when you feel sleepy, when you feel hungry, when your temperature rises and falls, when some hormones go up and down.

Circadian Circadian is是 a science-and-medicine word一個科學和醫學用的詞 for用來指 that follow跟隨 a roughly 24-hour pattern大約24小時規律的 things事物 — about one day也就是大約一天。 We use it most about the body我們最常用它來講身體: when you feel sleepy什麼時候想睡, when you feel hungry什麼時候肚子餓, when your temperature rises and falls體溫什麼時候升降, when some hormones go up and down有些荷爾蒙什麼時候起伏。

Doctors talk about your circadian rhythm, meaning that inner day-clock. It is not a clock you can see; it is a pattern your body keeps, even in a dark room, though actually light (especially morning light) is what keeps it lined up with the real day. Jet lag is what happens when you fly far and the sun’s day no longer matches your body’s day.

Doctors talk about醫生會說 your circadian rhythm你的「circadian rhythm」（生理節律）, meaning也就是指 that inner day-clock體內那個日夜時鐘。 It is not a clock you can see它不是一個看得到的時鐘; it is a pattern your body keeps而是身體一直維持的規律, even in a dark room就算在暗房裡也一樣, though actually不過其實 light (especially morning light)光線（尤其是早晨的光線） is what keeps it lined up with the real day才是讓它跟真實的一天對齊的東西。 Jet lag時差 is what happens指的是這種情況： when you fly far當你飛很遠、 and the sun's day no longer matches your body's day太陽的一天跟身體的一天不再對得上。

The word is fairly formal. Ordinary people more often say body clock. You will meet it in biology class, sleep ads, and hospital leaflets, not much in chat.

The word這個詞 is fairly formal算是滿正式的。 Ordinary people一般人 more often say更常說 body clock body clock（生理時鐘）。 You will meet it你會 in biology class在生物課、 sleep ads助眠廣告、 and hospital leaflets醫院的傳單裡都會看到它, not much in chat但很少在聊天中出現。

It does not mean “circular” or “going in a circle,” even though it looks a bit like those words. It means “about a day.”

It does not mean它不是指 "circular"「圓形的」 or "going in a circle,"或「繞圈子」 even though it looks a bit like those words雖然看起來有點像這些字。 It means它指的是 "about a day."「大約一天」