‘落伍’ literally means ‘to fall behind the ranks’ — ‘落’ (luò) means ‘to fall, drop, or lag’, and ‘伍’ (wǔ) originally referred to a military unit of five soldiers, symbolizing an organized group or collective standard. Together, the term metaphorically describes falling behind societal, technological, or ideological progress — becoming outdated, obsolete, or disconnected from current trends or norms.

It’s commonly used in formal or semi-formal contexts to describe people, ideas, methods, or institutions that no longer keep pace with modern developments — for example, outdated teaching methods, aging technology, or conservative mindsets. While it carries a mildly negative connotation, it’s not harshly critical; rather, it signals a need for renewal or adaptation. The phrase is often paired with subjects like ‘思想’ (thinking), ‘技术’ (technology), or ‘观念’ (concepts), and frequently appears in news reports, education discussions, and policy analyses.