CONTRACTILE
Con*tract"ile, a. Etym: [Cf. F. contractile.]

Defn: tending to contract; having the power or property of contracting, or of shrinking into shorter or smaller dimensions; as, the contractile tissues. The heart's contractile force. H. Brooke. Each cilium seems to be composed of contractile substance. Hixley. Contractile vacuole (Zoöl.), a pulsating cavity in the interior of a protozoan, supposed to be excretory in function. There may be one, two, or more.

CONTRACTILITY
Con`trac*til"i*ty, n.

1. The quality or property by which bodies shrink or contract.

2. (Physiol.)

Defn: The power possessed by the fibers of living muscle of contracting or shortening.

Note: When subject to the will, as in the muscles of locomotion, such power is called voluntary contractility; when not controlled by the will, as in the muscles of the heart, it is involuntary contractility.

CONTRACTION
Con*trac"tion, n. Etym: [L. contractio: cf. F. contraction.]

1. The act or process of contracting, shortening, or shrinking; the state of being contracted; as, contraction of the heart, of the pupil of the eye, or of a tendion; the contraction produced by cold.

2. (Math.)