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 décro?tre), 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.).
例文
1. If the egg is not fertilised oestrogen and progesterone decrease .
卵細胞が受精しないとエストロゲンと黄体ホルモンが低下する。
2.The prices of polymers and suchlike materials will decrease .
ポリマーおよび類似材料の価格が低下します。
3. The demand for tea is on the decrease ( each year ).
茶葉の需要量（年々）は減少している.
4.Last year there was a 20% decrease in his earnings.
昨年、彼の収入は20%減少した。
5.This shows a slight decrease on the numbers of the previous month.