When combined, 正常 (zhèngcháng) literally means “correctly common” or “standard and usual.” Adding the negation particle 不 (bù) at the beginning simply flips the meaning to “not normal” or “abnormal.”
While “不正常” can be a neutral, factual description (like for a machine), it carries significant weight when applied to people and social situations. Chinese culture often places a high value on harmony, conformity, and following established social norms.
“不正常” is extremely common in daily life and its connotation depends heavily on the context.