adjective

1. apt or likely to change or vary; changeable, inconstant, fickle, fluctuating, etc.
2. that can be changed or varied
3. Biol. tending to deviate in some way from the type; aberrant
4. Math. having no fixed value

Etymology: ME < MFr < L variabilis

noun

1. anything changeable; esp., a quality or quantity that varies or may vary
2. a shifting wind
3. Astron. variable star
4. Math., Physics
   1. a part of a mathematical expression that may assume any value in a specific, related set of values
   2. a symbol for such a part