The "Oxford English Dictionary" defines subsidiarity as "the principle that a central authority should have a subsidiary function, performing only those tasks which cannot be performed at a more local level". The concept is applicable in the fields of government, political science, neuropsychology, cybernetics, management and in military command (mission command). The OED adds that the term "subsidiarity" in English follows the early German usage of ""Subsidiarität"". More distantly, it is derived from the Latin verb "subsidio" (to aid or help), and the related noun "subsidium" (aid or assistance).