enlistment vs duty tour

enlistment and duty tour both are nouns.

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

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

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

enlistment (noun)	duty tour (noun)
the act of enlisting (as in a military service)	a period of time spent in military service
a period of time spent in military service