Definition
to not complete something as quickly as needed or within the designated timeframe
沒有跟上；落在後面
If you don't speed up, you will fall behind schedule.
如果你不加快速度，你將會落後於進度。
During exam season, students often fall behind due to stress.
在考試季節，學生常常因為壓力而落後。
The company has fallen behind its competitors technologically.
這家公司在技術上已經落後於競爭對手。