a. [ L. commensurabilis; pref. com- + mensurable. See Commensurate, and cf. Commeasurable. ] Having a common measure; capable of being exactly measured by the same number, quantity, or measure. -- Com*men"su*ra*ble*ness, n. [1913 Webster]

Commensurable numbers or
Commensurable quantities (Math.), those that can be exactly expressed by some common unit; thus a foot and yard are commensurable, since both can be expressed in terms of an inch, one being 12 inches, the other 36 inches. --
Numbers commensurable in power, or
Quantities commensurable in power, those whose squares are commensurable. [1913 Webster]

a. [ Pref. im- not + L. mensurabilis measurable: cf. F. immensurable. Cf. Immeasurable. ] Immeasurable. [ 1913 Webster ]

What an immensurable space is the firmament. Derham. [ 1913 Webster ]

a. [ Pref. in- not + commensurable: cf. F. incommensurable. ] Not commensurable; having no common measure or standard of comparison; as, quantities are incommensurable when no third quantity can be found that is an aliquot part of both; the side and diagonal of a square are incommensurable with each other; the diameter and circumference of a circle are incommensurable. [ 1913 Webster ]

They are quantities incommensurable. Burke.

-- In`com*men"su*ra*ble*ness, n. -- In`com*men"su*ra*bly, adv. [ 1913 Webster ]

n. One of two or more quantities which have no common measure. [ 1913 Webster ]

a. [ L. mensurabilis, fr. mensurare to measure, fr. mensura measure: cf. F. mensurable. See Measurable, Measure. ] Capable of being measured; measurable. [ 1913 Webster ]

n. The quality or state of being mensurable; measurableness. [ 1913 Webster ]