imposition vs burden

imposition and burden both are nouns.

Word	Noun	Adjective	Verb	Adverb
imposition	Yes	No	No	No
burden	Yes	No	Yes	No

As nouns, burden is a hypernym of imposition; that is, burden is a word with a broader meaning than imposition:

Other hypernyms of imposition include encumbrance, incumbrance, load, onus.

imposition (noun)	burden (noun)
the act of imposing something (as a tax or an embargo)	weight to be borne or conveyed
an uncalled-for burden	the central idea that is expanded in a document or discourse
	an onerous or difficult concern
	the central meaning or theme of a speech or literary work

imposition (verb)	burden (verb)
	impose a task upon, assign a responsibility to
	weight down with a load