tour of duty vs tour

tour of duty and tour both are nouns.

Word	Noun	Adjective	Verb	Adverb
tour of duty	Yes	No	No	No
tour	Yes	No	Yes	No

As nouns, tour of duty and tour are synonyms defined as:

Other synonyms of tour of duty include duty tour, enlistment, hitch, term of enlistment.

tour of duty (noun)	tour (noun)
a period of time spent in military service	a journey or route all the way around a particular place or area
	a time period for working (after which you will be relieved by someone else)
	a period of time spent in military service

tour of duty (verb)	tour (verb)
	make a tour of a certain place