demarcation vs dividing line

demarcation and dividing line both are nouns.

Word	Noun	Adjective	Verb	Adverb
demarcation	Yes	No	No	No
dividing line	Yes	No	No	No

As nouns, demarcation and dividing line are synonyms defined as:

Other synonyms of demarcation include contrast, line.

demarcation (noun)	dividing line (noun)
a conceptual separation or distinction	a conceptual separation or distinction
the boundary of a specific area