An Etymological Dictionary of Astronomy and Astrophysics

1. The act or process of forming or the state of being formed, such as → star formation.
   
2. Geology: A laterally continuous rock unit with a distinctive set of characteristics that make it possible to recognize and map from one → outcrop or well to another. The basic rock unit of stratigraphy.

Etymology (EN): Verbal noun of → form, + -ate + -ion.

Etymology (PE): Diseš, verbal noun of disidan, → from dis-, → form, + -eš.