quarter-circle vs quadrant

quarter-circle and quadrant both are nouns.

Word	Noun	Adjective	Verb	Adverb
quarter-circle	Yes	No	No	No
quadrant	Yes	No	No	No

As nouns, quarter-circle and quadrant are synonyms defined as:

quarter-circle (noun)	quadrant (noun)
a quarter of the circumference of a circle	a measuring instrument for measuring altitude of heavenly bodies
	the area enclosed by two perpendicular radii of a circle
	any of the four areas into which a plane is divided by two orthogonal coordinate axes
	a quarter of the circumference of a circle