'通宵' literally combines '通' (tōng), meaning 'through' or 'entire', and '宵' (xiāo), meaning 'night' or 'evening'. Together, they form an adverb meaning 'all night long' — emphasizing continuous activity or duration from evening until dawn. It is commonly used to describe staying awake, working, studying, celebrating, or traveling without sleeping through the night.

This word carries a slight connotation of effort, exhaustion, or intensity — for instance, pulling an all-nighter implies dedication or urgency. While it can appear after verbs ('熬夜通宵'), it most frequently functions as a standalone adverb before or after the verb ('通宵学习', '工作到通宵'). It is neutral in register but often implies informality or personal experience rather than formal documentation.