burden vs dead weight

burden and dead weight both are nouns.

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

As nouns, dead weight is a hyponym of burden; that is, dead weight is a word with a more specific, narrower meaning than burden:

Other hyponyms of burden include fardel, imposition, pill.

burden (noun)	dead weight (noun)
weight to be borne or conveyed	a heavy motionless weight
the central idea that is expanded in a document or discourse	an oppressive encumbrance
an onerous or difficult concern
the central meaning or theme of a speech or literary work

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