duty vs duty assignment

duty and duty assignment both are nouns.

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

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

duty: work that you are obliged to perform for moral or legal reasons
duty assignment: a duty that you are assigned to perform (especially in the armed forces)

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

duty (noun)	duty assignment (noun)
the social force that binds you to the courses of action demanded by that force	a duty that you are assigned to perform (especially in the armed forces)
work that you are obliged to perform for moral or legal reasons
a government tax on imports or exports