burden vs overwhelm

burden is a noun but overwhelm is not a noun.

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

As verbs, overwhelm is a hyponym of burden; that is, overwhelm is a word with a more specific, narrower meaning than burden:

Other hyponyms of burden include overburden, bear down, deluge, flood out, adjure.

burden (noun)	overwhelm (noun)
weight to be borne or conveyed
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

burden (verb)	overwhelm (verb)
impose a task upon, assign a responsibility to	charge someone with too many tasks
weight down with a load	overcome by superior force
	cover completely or make imperceptible
	overcome, as with emotions or perceptual stimuli