哆嗦 (duō suo) is a colloquial verb meaning 'to tremble/shiver', typically from cold or fear, emphasizing small, continuous shaking. 颤抖 (chàn dǒu) is its more formal, literary counterpart used in writing. 哆嗦 and 发抖 (fā dǒu) are very close in usage, but 哆嗦 often suggests a finer, more uncontrollable tremor.