pole star vs variable

pole star and variable both are nouns.

Word	Noun	Adjective	Verb	Adverb
pole star	Yes	No	No	No
variable	Yes	Yes	No	No

pole star (noun)	variable (noun)
the brightest star in Ursa Minor; at the end of the handle of the Little Dipper; the northern axis of the earth points toward it	a quantity that can assume any of a set of values
	a symbol (like x or y) that is used in mathematical or logical expressions to represent a variable quantity
	something that is likely to vary; something that is subject to variation
	a star that varies noticeably in brightness

pole star (adjective)	variable (adjective)
	liable to or capable of change
	(used of a device) designed so that a property (as e.g. light) can be varied
	marked by diversity or difference