In a chemistry lab, a reagent is a substance you add on purpose because it will react, and that reaction tells you something — often that another substance is there, or how much of it there is.

In a chemistry lab在化學實驗室裡 a reagent是reagent(試劑) is a substance you add on purpose because it will react是你刻意加進去的一種物質,因為它會發生反應 and that reaction tells you something而那個反應會告訴你一些訊息 often that another substance is there常常是告訴你有另一種物質存在 or how much of it there is或它的量有多少

A school-book picture: you drop a reagent into a liquid, the colour changes, and that change is the answer. That “testing” use is the one learners meet first.

A school-book picture教科書上的畫面是 you drop a reagent into a liquid你把一種reagent滴進液體裡 the colour changes顏色就會改變 and that change is the answer而那個變化就是答案 That “testing” use is the one learners meet first這種「檢測」用法是學習者最先碰到的

Though actually, chemists also stretch reagent to mean almost any chemical they put into a reaction, not only the one that “shows” something; in that wider talk it sits near reactant (a thing that gets used up in the reaction).

Though actually不過其實 chemists also stretch reagent to mean almost any chemical they put into a reaction化學家也會把reagent這個字用得更廣,幾乎指他們放進反應裡的任何化學物質 not only the one that “shows” something而不只是那個「顯示」出結果的物質 in that wider talk在這種比較廣義的說法裡 it sits near reactant (a thing that gets used up in the reaction)它跟reactant(反應物,也就是反應中被消耗掉的東西)意思相近

It is a lab and textbook word, not a kitchen word.

It is a lab and textbook word這是一個實驗室和教科書用字 not a kitchen word而不是廚房裡會用的字