dead weight vs burden

dead weight and burden both are nouns.

Word	Noun	Adjective	Verb	Adverb
dead weight	Yes	No	No	No
burden	Yes	No	Yes	No

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

Other hypernyms of dead weight include encumbrance, incumbrance, load, onus.

dead weight (noun)	burden (noun)
a heavy motionless weight	weight to be borne or conveyed
an oppressive encumbrance	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

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