duty vs task

duty and task both are nouns.

Word	Noun	Adjective	Verb	Adverb
duty	Yes	No	No	No
task	Yes	No	Yes	No

As nouns, task is a hyponym of duty; that is, task is a word with a more specific, narrower meaning than duty:

duty: work that you are obliged to perform for moral or legal reasons
task: a specific piece of work required to be done as a duty or for a specific fee

Other hyponyms of duty include chore, job, function, office, part, role, assignment, duty assignment.

duty (noun)	task (noun)
the social force that binds you to the courses of action demanded by that force	a specific piece of work required to be done as a duty or for a specific fee
work that you are obliged to perform for moral or legal reasons	any piece of work that is undertaken or attempted
a government tax on imports or exports

duty (verb)	task (verb)
	use to the limit
	assign a task to