fall是什么意思？

　　They announced a fall in pretax profits.

　　他们宣布了税前利润的下降。

　　Large flakes of snow began swiftly to fall.

　　大片大片的雪花开始飞快地落下。

　　House prices could perk up during the fall.

　　秋季房价可能会上涨。