How do you spell Quadruple

Available Definitions:
1)  a. - Fourfold; as, to make quadruple restitution; a quadruple alliance.
2)  n. - four times the sum or number; a fourfold amount; as, to receive to quadruple of the amount in damages.
3)  v. t. - To multiply by four; to increase fourfold; to double; to double twice.
4)  v. i. - To be multiplied by four; to increase fourfold; to become four times as much.