What is "body of interest" in Chinese? I can't find any appropriate translation for "body of interest" on the Internet. It's about something you draw on the first step when you try to solve a machenical engineering problem by doing a FBD (Free Body Diagram) where simplified shapes represent parts of a machine. What I got from the Internet is "利益主体". But apparently, it's not something about profit since it's related to engineering machenics. "An FBD represents the body of interest and the external forces on it." This is what I found on Wikipedia. But since the Chinese site is banned in China, there is no way to find out how to say it precisely in Chinese. Can someone who's familiar to this subject help me? The definition of it in English will also do. Thanks.