When it comes to storing files, the term "master file" can be used to refer to the primary copy of a file that serves as a source of truth. However, there are several other synonyms that can also be used depending on the context of the files being stored. For example, a "core file" or "central file" might be used to describe the main file that holds critical data or information. In the context of project management, a "leading file" or "primary file" might be used to describe the main document that guides the project. Ultimately, the key is to choose a term that best conveys the importance and centrality of the file in question.