orbital

The word 'orbital' is a modern scientific formation built upon the classical Latin noun orbita, which originally meant the track or rut made by a wheel. This sense of a circular path was metaphorically extended in astronomy to describe the regular, repeating course of a celestial body. The adjectival suffix -alis (English -al) was appended to create a term meaning 'pertaining to an orbit.' In the mid-20th century, this astronomical term was borrowed into atomic physics to describe the region of space where an electron is likely to be found, and into British urban planning to designate a major circumferential road.

Structure: orbit (path) + al (adjective suffix) orbit (from Latin orbita, meaning track, rut, course); al (from Latin adjectival suffix -alis, meaning of or pertaining to).