ev·o·lu·tion 
(ĕv′ə-lshən, ē′və-)
(ĕv′ə-lshən, ē′və-)n.
1.
a. A gradual process in which something changes into a different and usually more complex or better form.
b. A result of this process; a development: Judo is an evolution of an earlier martial art.
2. Biology
a. Change in the genetic composition of a population during successive generations, often resulting in the development of new species. The mechanisms of evolution include natural selection acting on the genetic variation among individuals, mutation, migration, and genetic drift.
b. The historical development of a related group of organisms; phylogeny.
3. Astronomy Change in the structure, chemical composition, or dynamical properties of a celestial object or system such as a planetary system, star, or galaxy. Evolution often changes the observable or measurable characteristics of the object or system.
4. A movement that is part of a set of ordered movements: naval evolutions in preparation for battle.
5. Mathematics The extraction of a root of a quantity.
[Latin ēvolūtiō, ēvolūtiōn-, from ēvolūtus, past participle of ēvolvere, to unroll; see EVOLVE.]
ev′o·lution·al, ev′o·lution·ar′y (-shə-nĕr′ē) adj.
ev′o·lution·ar′i·ly adv.