恶习 (è xí) literally combines 恶 (è), meaning 'bad', 'evil', or 'unpleasant', and 习 (xí), meaning 'habit' or 'practice'. Together, it refers to a deeply ingrained, harmful behavior that is difficult to break—such as smoking, excessive gambling, procrastination, or speaking rudely. Unlike neutral habits (习惯), 恶习 carries strong negative moral or health connotations and implies long-term damage to oneself or others.

This term is commonly used in formal advice, education, and self-improvement contexts. Parents might warn children against developing 恶习; teachers discuss them in character education; doctors cite them when counseling patients on lifestyle changes. It’s not used for minor quirks or temporary behaviors—it suggests persistence, resistance to change, and social disapproval. The word often appears with verbs like 改掉 (to get rid of), 克服 (to overcome), or 染上 (to pick up).