A physics TA is trying to help a student through a problem: TA: "OK, what is this length here?" (pointing to line on diagram) Student: "Ummm.... x-naught?" TA: "No...." Student: "Sure it's not x-naught?" TA: "Yes, I'm sure." Student: (confused) "Ummm.... Why not?" TA: "y-naught, very good..."
(From the "Rest" of RHF)