名詞 fall off:

1. a noticeable deterioration in performance or quality
   同義詞：slump, slack, drop-off, falloff, falling off

動詞 fall off:

1. come off
2. fall heavily or suddenly; decline markedly
   同義詞：slump, sink
3. diminish in size or intensity
   同義詞：fall away

1. It used to be my favourite restaurant but the standard of cooking has fallen off recently.
   那是我以前最喜歡的飯館，但近來烹飪水平已大不如前了。
2. Be careful not to fall off the ladder.
   當心別從梯子上掉下來。
3. One slip and you could fall off the cliff.
   腳下一滑就可能從懸崖上跌下去。