Nouns

(n)variablesomething that is likely to vary; something that is subject to variation“the weather is one variable to be considered”
(n)variable, variable quantitya quantity that can assume any of a set of values
(n)variable star, variablea star that varies noticeably in brightness
(n)variablea symbol (like x or y) that is used in mathematical or logical expressions to represent a variable quantity

Adjectives

(a)variableliable to or capable of change“rainfall in the tropics is notoriously variable”, “variable winds”, “variable expenses”
(s)varying, variablemarked by diversity or difference“the varying angles of roof slope”, “nature is infinitely variable”
(s)variable(used of a device) designed so that a property (as e.g. light) can be varied“a variable capacitor”, “variable filters in front of the mercury xenon lights”