-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.