a general name for materials combining calcium with carbonates, oxides or hydroxides; the name comes from a root "sticking or adhering"; its earliest use was as mortar for construction. Water has several systematic names, including oxidane (the IUPAC name), hydrogen oxide, and dihydrogen monoxide (DHMO). The latter was the basis of the dihydrogen monoxide hoax, a document that was circulated warning readers of the dangers of the chemical (for example, it is fatal if inhaled). Organic chemistry In organic chemistry, some trivial names derive from a notable property of the thing being named. For instance, lecithin, the common name for phosphatidylcholine, was originally isolated from egg yolk. The word is coined from the Greek λέκιθος (lékithos) for yolk. Many trivial names continue to be used because their sanctioned equivalents are considered too cumbersome for everyday use. For example, "tartaric acid", a compound found in wine, has a systematic name of 2,3-dihydroxybutanedioic acid. The pigment β-Carotene has an IUPAC name of 1,3,3-trimethyl-2-[(1E,3E,5E,7E,9E,11E,13E,15E,17E)-3,7,12,16-tetramethyl-18-(2,6,6-trimethylcyclohexen-1-yl)octadeca-1,3,5,7,9,11,13,15,17-nonaenyl]cyclohexene. However, the trivial name can be potentially confusing. Based on its name, one might come to the conclusion that the molecule theobromine contains one or more bromine atoms. In reality it is an alkaloid similar in structure to caffeine. Shape-based Several organic molecules have semitrivial names where the suffixes -ane (for an alkane) or -ene (for an alkene) are added to a name based on the shape of the molecule. Some are pictured below. Other examples include barrelene (shaped like a barrel), fenestrane (having a window-pane motif), ladderane (a ladder shape), olympiadane (having a shape with the same topology as the Olympic rings) and quadratic acid (also known as squaric acid). Based on fiction The bohemic acid complex is a mixture of chemicals obtained through fermentation of a species of actinobacteria. In 1977 the components were isolated and have been found useful as antitumor agents and anthracycline antibiotics. The authors named the complex (and one of its components, bohemamine) after the opera La bohème by Puccini, and the remaining components were named after characters in the opera: alcindoromycin (Alcindoro), collinemycin (Colline), marcellomycin (Marcello), mimimycin (Mimi), musettamycin (Musetta), rudolphomycin (Rodolfo) and schaunardimycin (Schaunard). However, the relationships between the characters do not correctly reflect the chemical relationships. A research lab at Lepetit Pharmaceuticals, led by Piero Sensi, was fond of coining nicknames for chemicals that they discovered, later converting them to a form more acceptable for publication. The antibiotic rifampicin was