1. Different positioning: keywords are a new vocabulary of information retrieval language, which are used to describe the theme of documents and give the retrieval of documents, and keywords are the key theme content of documents.

2. Different functions: Subject words are words or phrases that distinguish things according to the characteristic relationship of concepts, and are used to accurately express the dynamic semantic concept relationship between words, while keywords refer to the vocabulary used by a single media when making and using indexes, which is a vocabulary in library science.