Refers to a drop in quantity, number, or degree. Often used in compound nouns like 人口減り (population decline) or 売上減り (sales drop).
The decrease in rain is noticeable this summer.
The decline in sales continues.
loss in quantity; shrinkage; ullage · decrease in value; erosion of value
Noun form of the verb 減る (へる, 'to decrease'), from Old Japanese. The kanji 減 means 'decrease' or 'diminish'.