One of the standard Western diatonic modes. The name "aeolian" was not used by the ancient Greeks, and was first employed by Glareanus in Dodecachordon (1547).
The diatonic genus of the aeolian mode equates to the 8ve-species from A to A, in ascending order thus ("t" means "tone" in the sense of "whole-tone", and "s" means semitone):
A B C D E F G A t s t t s t t
Note that the various ancient Greek modes had variant interval structures, depending on the genus and shade.
The aeolian mode is synonymous with the "natural minor scale".