variable quantity vs quantity

variable quantity and quantity both are nouns.

Word	Noun	Adjective	Verb	Adverb
variable quantity	Yes	No	No	No
quantity	Yes	No	No	No

As nouns, quantity is a hypernym of variable quantity; that is, quantity is a word with a broader meaning than variable quantity:

variable quantity: a quantity that can assume any of a set of values
quantity: the concept that something has a magnitude and can be represented in mathematical expressions by a constant or a variable

variable quantity (noun)	quantity (noun)
a quantity that can assume any of a set of values	how much there is or how many there are of something that you can quantify
	an adequate or large amount
	the concept that something has a magnitude and can be represented in mathematical expressions by a constant or a variable