An Etymological Dictionary of Astronomy and Astrophysics

Any process of formation or growth; development; a process of gradual, progressive change; a product of such development; something evolved.
Astro.: A continuous and progressive change according to certain laws and by means of acting physical forces.
Biology: A process of development in which a living organism,
through major environmental changes, becomes more and more complex by the differentiation of its parts.

See also: Verbal noun of → evolve.