‘疯子’ literally combines 疯 (fēng), meaning 'crazy' or 'insane', and 子 (zi), a common noun suffix that turns adjectives or verbs into informal, often colloquial nouns—similar to English '-er' or '-ist'. Together, it means 'a crazy person', but it’s not clinical; it’s used casually, sometimes playfully or teasingly, and often carries mild judgment or affection depending on tone and context.

This word appears frequently in everyday speech—among friends joking about impulsive behavior ('He bought ten pairs of shoes online—what a疯子!'), in media describing eccentric characters, or even self-deprecatingly ('I stayed up until 4 a.m. studying—I’m such a疯子!'). While not inherently offensive, it can sound harsh if used seriously toward someone with mental illness, so sensitivity is important. It’s rarely used in formal writing or medical contexts, where terms like 精神病患者 (jīngshénbìng huànzhě) are appropriate instead.