THE first use of the prefix `nor' appears to be in a paper by Matthiessen and Foster1 published in 1868. They were studying the nitrogen-free substance opianic acid formed by the oxidation of narcotine and obtained evidence that it contained two methyl groups. They had used the term `normal opianic acid' to mean the completely demethylated compound, and they then used the contraction `methylnoropianic acid' for the monomethyl derivative. Since that time the prefix has generally been used to denote the replacement of one or more methyl groups by H, or the disappearance of CH2 from a carbon chain, but its use may leave the resulting structure in doubt. I apologize for supporting a false etymological theory.