A preservative is a chemical that prevents things from decaying. Some preservatives are added to food, and others are used to treat wood or metal.
例句
Nitrates are used as preservatives in food manufacture...硝酸鹽在食品加工業中被用作防腐劑。Though the panels come pre-treated, they needed a final sealing with two coats of preservative.雖然這些鑲板運來時經過了預處理，但是還需要涂上兩層防腐劑進行最后的密封。