decision vs assignment

decision and assignment both are nouns.

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

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

Other hyponyms of decision include appointment, designation, naming, call, move, casting lots, drawing lots, sortition, resolution.

decision (noun)	assignment (noun)
the act of making up your mind about something	a duty that you are assigned to perform (especially in the armed forces)
the trait of resoluteness as evidenced by firmness of character or purpose	the act of putting a person into a non-elective position
a position or opinion or judgment reached after consideration	the act of distributing something to designated places or persons
the outcome of a game or contest	an undertaking that you have been assigned to do (as by an instructor)
(boxing) a victory won on points when no knockout has occurred	the instrument by which a claim or right or interest or property is transferred from one person to another
	(law) a transfer of property by deed of conveyance