random variable vs variable

random variable and variable both are nouns.

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

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

Other hypernyms of random variable include variable quantity.

random variable (noun)	variable (noun)
a variable quantity that is random	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

random variable (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