Q: What word describes redundancies like "PIN number"? "Advanced planning"?
A: Pleonasm. A pleonasm consists of two concepts (usually two words) that are redundant. What does "redundant" mean? Well, how about "more than enough; overabundant; excess; and superfluous"? Still having a problem understanding what pleonasm means? Some pleonastic expressions are also known as tautologies. Tautology means, "needless repetition of an idea in a different word, phrase, or sentence; redundancy; pleonasm." What about pleonasm? It means, "the use of more words than are necessary for the expression of an idea; redundancy." So it is that we go around in circles: pleonasm means tautology, which means redundancy, which means pleonasm, which means tautology, ad infinitum.