1、“落后”在英文中可以這么寫：fall behind；lag behind；backward。

2、例句：

（1）“落在后面”：fall behind；lag behind

Be modest and prudent，never lag behind！謙虛謹(jǐn)慎，永不落后！

Put on a spurt，or you'll fall behind。加把勁，不然你要落后了。

（2）“不先進(jìn)”：backward

Put an end to the backwardness of the mountainous areas。改變山區(qū)落后面貌.