variable

(noun) something that is likely to vary; something that is subject to variation. Example: "The weather is one variable to be considered."

(noun) a quantity that can assume any of a set of values. Synonyms: variable quantity.

(noun) a star that varies noticeably in brightness. Synonyms: variable star.

(noun) a symbol (like x or y) that is used in mathematical or logical expressions to represent a variable quantity.

(adj) liable to or capable of change. Synonyms: variable (vs. invariable). Examples: "Rainfall in the tropics is notoriously variable." "Variable winds." "Variable expenses."

(adj) marked by diversity or difference. Synonyms: varying. Examples: "The varying angles of roof slope." "Nature is infinitely variable."

(adj) (used of a device) designed so that a property (as e.g. light) can be varied. Examples: "A variable capacitor." "Variable filters in front of the mercury xenon lights."