but-

Also butyro‑.

Four-carbon chains of atoms.

The first element of English butryic, from Latin butyrum, butter.

The first chemical compound named from this Latin source was butyric acid, C₃H₇COOH, a colourless organic acid, so named because it was found in rancid butter. Names for other four-carbon compounds have since been created, such as the hydrocarbons butane, butadiene, and butylene, and the organic alcohol butanol. The adjective is butyl, in reference to the radical C₄H₉—, as in butyl rubber and in butyl acetate, an important solvent in lacquers.

The longer form butyro‑ is now relatively uncommon, but appears, for example, in butyrophenone, one of a small group of tranquillizers used to relive symptoms of serious psychiatric disorders. A butyrometer is an instrument for estimating the percentage of butter-fat in milk.