即时 (jí shí) means 'immediately, instantly' and emphasizes that an action happens at the very moment it is triggered, often in technical or formal contexts. It is more specific than 立刻 or 立即, which simply mean 'right away' without the connotation of real-time response. 实时 (shí shí) is similar but focuses on continuous real-time processing (e.g., 实时直播 'live broadcast'), while 即时 is for a single immediate action.