In rhetoric, a tautology (from Greek ταὐτός, "the same" and λόγος, "word/idea") is a logical argument constructed in such a way, generally by repeating the same concept or assertion using different phrasing or terminology, that the proposition as stated is logically irrefutable, while obscuring the lack of evidence or valid reasoning supporting the stated conclusion.
Rhetorical tautology vs. circular reasoning
Circular reasoning differs from tautologies in that circular reasoning restates the premise as the conclusion, instead of deriving the conclusion from the premise. (This is often conflated with begging the question, in which the premise relies on the assumption of the conclusion). A tautology simply states the same thing twice.
Rhetorical tautologies typically present themselves as redundancies only comprising part of a statement.