I spent a chunk of the morning (chunk o' the morning to you!) researching the distinction between a rhetorical tautology and a pleonasm.  It wasn't as much fun as it sounds.

For the record, a tautology (in the rhetorical, not the logical sense) is a restatement of the same concept in different words.  Essentially, just a repetition.  By contrast, a pleonasm is a pair of expressions (words, phrases, etc.) which do not mean the same thing, but where one is implicit in the other.  For example, "a round circle" is a pleonasm rather than a tautology.  The words "round" and "circle" do not mean the same thing, but the concept of "round" is implicit in the use of the word "circle."  A "radially equidistant circle" would be more like a tautology, since a circle can be defined as a set of points that are radially equidistant from a central point.

Tags: department of redundancy department, language