落后用英文表示为：backward， fall behind。backward的英式发音为 [ˈbækwəd] ，美式发音为 [ˈbækwərd]。意思是：落后的，向后的，反向的，怯生生的。
fall behind的英式发音为 [fɔ:l biˈhaind]，美式发音为 [fɔl bɪˈhaɪnd] 。意思是：落后，下降，退后，逾期（付款等）。
拓展资料
backward的用法
1、He unlocked the door of apartment two and disappeared inside after a backward glance at Larry
他打开2号公寓的门，回头瞥了拉里一眼，然后就进了房间。
2、At a certain age, it's not viable for men to take a backward step into unskilled work
到了一定的年龄，就不可能再退回去干不需要技能的工作。
3、We need to accelerate the pace of change in our backward country.
我们应当为落后的祖国加快变革的脚步。
4、I was slow to walk and talk and my parents thought I was backward.
我学走路和说话都很慢，所以我父母以为我很迟钝。
5、He did a backward flip.
他做了一个后空翻。
fall behind的用法
1、Put on a spurt, or you'll fall behind.
加把劲，不然你要落后了。
2、When the revolution is developing rapidly, some people are bound to fall behind.
在革命急速发展的时候，总不免有人要落伍的。
3、If you don't come to class regularly, you will fall behind in your studies.
如果你经常不来上课，学习成绩就会落在别人后面。
4、If your payments of rent fall behind, you will be asked to leave.
如果你不如期交房租，你就会被撵走。
5、One will fall behind the times if one does not acquire new knowledge.
不及时充电，更新知识，就会落后于时代。