The words "know","understand" and "understand" had certain similarities in their expressions, but there were also some differences: 1. The difference in degree: " Know " means that you have a certain understanding and recognition of something but not necessarily very clear;" Understand " means that you have a deeper understanding of something and that your understanding is very clear;" Understand " means that you have a complete understanding of something, understand it, and think deeply about it. 2. The difference in scope: the scope of "know" is broader and can include understanding and understanding of many things; the scope of "know" is narrower than "know" and usually only involves a specific field or topic; the scope of "understand" is narrower and only involves a specific problem or thing. 3. Different usages: "know" and "understand" can usually be used to express the understanding and knowledge of something, but "understand" is more often used to emphasize the in-depth study of a certain field, while "understand" is more often used to express the deep understanding and knowledge of a certain problem or thing. The words "know","understand", and "understand" had some similarities in their expressions, but there were also some differences. The exact words used depended on the context and the intention of the expression.