-ine

-ine is a suffix used in chemistry to denote two kinds of substance. The first is a chemically basic and alkaloidal substance. It was proposed by Joseph Louis Gay-Lussac in an editorial accompanying a paper by Friedrich Sertürner describing the isolation of the alkaloid "morphium", which was subsequently renamed to "morphine". Examples include quinine, morphine and guanidine. The second usage is to denote a hydrocarbon of the second degree of unsaturation. Examples include hexine and heptine. With simple hydrocarbons, this usage is identical to the IUPAC suffix -yne.

In common and literary adjectives (e.g. asinine, canine, feline, ursine), the suffix is usually pronounced or in some words alternatively. For demonyms (e.g. Levantine, Byzantine, Argentine) it is usually or. But in chemistry, it is usually pronounced or  depending on the word it appears in and the accent of the speaker. In a few words (for example, quinine, iodine and strychnine), the sound is normal in some accents. Gasoline ends with ; glycerine more often with than with. In caffeine, the suffix has merged with the e in the root, for stressed ; in gasoline and margarine as well the suffix is stressed by some people.

Some elements of the periodic table (namely the halogens, in the Group 17) have this suffix: fluorine (F), chlorine (Cl), bromine (Br), iodine (I) and astatine (At), ending which was continued in the artificially created tennessine (Ts).

The suffix -in is etymologically related and overlaps in usage with -ine. Many proteins and lipids have names ending with -in: for example, the enzymes pepsin and trypsin, the hormones insulin and gastrin, and the lipids stearin (stearine) and olein.