Quick definitions from WordNet (burden)

▸ noun:  an onerous or difficult concern ("The burden of responsibility")
▸ noun:  the central idea that is expanded in a document or discourse
▸ noun:  weight to be borne or conveyed
▸ noun:  the central meaning or theme of a speech or literary work
▸ verb:  weight down with a load
▸ verb:  impose a task upon, assign a responsibility to
▸ name:  A surname (common: 1 in 20000 families; popularity rank in the U.S.: #2327)

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▸ Also see burden