• vi. 衰退，[核] 衰減；腐爛，腐朽
• n. 衰退，[核] 衰減；腐爛，腐朽
• vt. 使腐爛，使腐敗；使衰退，使衰落
• n. (Decay)人名；(法)德凱

de-, 向下。-cay, 同-cad, 掉落，詞源同case, accident. 引申義腐爛。

decay

decay: [15] The notion underlying decay and its close relative decadence is of a ‘falling off’ from a condition of health or perfection. Decay comes from Old Northern French decair, a descendant of Vulgar Latin *dēcadere, which in turn came from Latin dēcidere, a compound verb formed from the prefix dē- ‘down, off, away’ and cadere ‘fall’ (source of English case and a wide range of related words). Decadence [16] was acquired via the medieval derivative dēcadentia. To the same word-family belongs deciduous [17], from Latin dēciduus, literally denoting the ‘falling off’ of leaves from trees.
=> accident, case, chance, decadence, deciduous

decay (v.)

late 15c., "to decrease," from Anglo-French decair, Old North French decair (Old French decheoir, 12c., Modern French déchoir) "to fall, set (of the sun), weaken, decline, decay," from Vulgar Latin *decadere "to fall off," from de- (see de-) + Latin cadere "to fall" (see case (n.1)). Meaning "decline, deteriorate" is c. 1500; that of "to decompose, rot" is from 1570s. Related: Decayed; decaying.

decay (n.)

mid-15c., "deterioration, decline in value," from decay (v.). Meaning "gradual decrease in radioactivity" is from 1897.

1. When not removed, plaque causes tooth decay and gum disease.

牙斑如果不清除就會導致牙齒蛀蝕和牙齦疾病。

來自柯林斯例句

2. There are problems of urban decay and gang violence.

存在城市衰敗和幫派暴力的問題。

來自柯林斯例句

3. The phosphate was deposited by the decay of marine microorganisms.

海洋微生物腐爛后沉積形成磷酸鹽。

來自柯林斯例句

4. The landlord had let the building fall into decay .

房東不管，房子已經破爛不堪。

來自《權威詞典》

5. The decay of the meat could have been prevented by proper refrigeration.

如果經過適當的冷藏,這些肉本來不至于腐爛掉.

來自《簡明英漢詞典》