variable vs varying

variable is a noun but varying is not a noun.

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

As adjectives, variable and varying are synonyms defined as:

variable (noun)	varying (noun)
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

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