- 刀不磨要生锈，人不学要落后 dāobùmóyàoshēngxiù, rénbùxuéyàoluòhòu continuous learninga blade will get rusty if it is not sharpened; a man will fall behind if he doesn't study
- 经济落后 jīngjìluòhòu underdevelopedeconomically backward
- 虚心使人进步，骄傲使人落后 xūxīnshǐrénjìnbù, jiāo'àoshǐrénluòhòu modesty leads progressmodesty leads to progress, while arrogance causes one to fall behind (a famous quote by Mao Zedong)