-gen

Also ‑gene, ‑geny, ‑genics, ‑genicity, and ‑genic.

Generation or creation.

Via French ‑gène from Greek genos, a kind.

The ending ‑gen can denote substances from which others are generated: glycogen (Greek glukus, sweet), a polysaccharide in body tissues that yields glucose on hydrolysis; collagen (Greek kolla, glue), the main structural protein found in animal connective tissue, which yields gelatin when boiled. It can also indicate substances which cause or induce some effect: carcinogen, a substance capable of causing cancer in living tissue; pathogen (Greek pathos, suffering or disease), a micro-organism that can cause disease. The first examples were names for gaseous chemical elements borrowed from French, of which two are hydrogen (Greek hudōr, water, so literally ‘water-maker’), and nitrogen (Greek nitron, nitre or saltpetre), a gaseous element, so named because it combines to form nitrates.

Examples formed using ‑gene include indigene (Latin indigina, a native, from gignere, to beget), a person native to a place, and phosgene, a poisonous gas (Greek phōs, light; it was first produced using sunlight). Gene, a sequence of nucleotides forming part of a chromosome, ultimately comes from the same Greek root. Some words ending in ‑gene are regarded as compounds of this word rather than examples of the ending, such as oncogene (Greek onkos, mass), a gene which can transform a cell into a tumour cell.

Nouns in ‑geny refer to the origin or development of something, or the mode by which it is produced: cosmogeny (Greek kosmos, order, world), the origin or evolution of the universe; orogeny (Greek oros, mountain), the process of forming a mountain range. They can sometimes refer also to the study of the processes involved, though for most there are related terms in ‑ology (see ‑logy), or a few in ‑genics, such as cryogenics (Greek kruos, frost), the branch of physics concerned with the production and effects of very low temperatures.

The adjectival ending ‑genic has a distinct sense of being well suited to something. The first example was photogenic in the 1920s—literally ‘producing or emitting light’, but used figuratively to mean a person who photographed well. By imitation it has since given rise to telegenic, mediagenic, and others.