'退步' (tuì bù) literally means 'to step back' — combining 退 ('to retreat, withdraw') and 步 ('step, pace'). As a noun, it refers to a decline or setback in ability, performance, health, or progress; as a verb, it describes the act of regressing or deteriorating. It’s commonly used to describe measurable declines — for example, in academic grades, physical fitness, language skills, or emotional well-being. Unlike neutral terms like 'change', 退步 carries a negative connotation, implying loss of ground previously gained.

The word appears frequently in feedback, self-reflection, and evaluations — especially in educational, professional, or health-related contexts. It is not used for temporary or minor fluctuations but for noticeable, sustained deterioration. While it can be used transitively (e.g., '他的听力退步了'), it’s most often intransitive and doesn’t take an object. The phrase is formal enough for written reports but also common in everyday speech when expressing concern about declining conditions.