The word "power" can have different connotations depending on the context in which it is used. When it comes to the legal realm, the term "power for first signature" refers to the authority granted to a person to sign a document on behalf of another individual or entity. In this case, some synonyms for the word "power" could be authorization, permission, consent, or endorsement. These terms all encompass the idea of giving someone the ability to act on behalf of another in a legal capacity. It's important for individuals to have a clear understanding of the power they are given, as any misuse or abuse can have serious legal consequences.