de-, 向下。-cre, 创造，增加，词源同create, crescent.

decrease

decrease: [14] Etymologically, decrease means ‘ungrow’. It comes from de(s)creiss-, the present stem of Old French de(s)creistre, which was a descendant of Vulgar Latin discrēscēre. This was an alteration of Latin dēcrēscēre, a compound verb formed from the prefix dē-, denoting reversal of a previous condition, and crēscēre ‘grow’ (source of English crescent and a wide range of other words).
=> crescent, croissant, increase

decrease (v.)

late 14c., from Anglo-French decreiss-, present participle stem of decreistre, Old French descroistre (12c., Modern French décroître), from Latin decrescere "to grow less, diminish," from de- "away from" (see de-) + crescere "to grow" (see crescent). Related: Decreased; decreasing.

decrease (n.)

late 14c., "detriment, harm;" early 15c. as "a becoming less or smaller," from Anglo-French decres; see decrease (v.).

1. If the egg is not fertilised oestrogen and progesterone decrease.

如果卵细胞没有受精，雌激素和黄体荷尔蒙就会下降。

来自柯林斯例句

2. The prices of polymers and suchlike materials will decrease.

聚合物及类似材料的价格会下降。

来自柯林斯例句

3. The demand for tea is on the decrease ( each year ).

茶叶的需求量 ( 逐年 ) 递减.

来自《现代汉英综合大词典》

4. Last year there was a 20 % decrease in his earnings.

去年他的收入减少了20%.

来自《现代汉英综合大词典》

5. This shows a slight decrease on the numbers of the previous month.

这表明比前一个月的数目略有减少.

来自《现代英汉综合大词典》