Definition of soldier for Students. : a person in military service and especially an enlisted person who is in the army.
Zeitgeist is defined as the spirit of a generation or a period of time. An example of zeitgeist is the free love and progressive thinking of the 1960s. the spirit of the age; trend of thought and feeling in a period. Origin of zeitgeist.
Charles Darwin 's theory of Natural Selection is one of the more common psychological adaptations to be studied in history. His ideas began the understanding of adaptation due to survival. The idea of Zeitgeist also has a way of explaining psychological adaptation.