Emily Dickinson Lexicon

COM-MEN'SU-RA-BLE, a. [Fr. from con and L. mensura, measure. See Measure.]

That have a common measure; reducible to a common measure. Thus a yard and a foot are commensurable, as both may be measured by inches. Commensurable numbers are those which may be measured or divided by another number without a remainder; as, 12 and 18, which may be measured by 6 and 3. Commensurable surds are those which, being reduced to their least terms, become true figurative quantities of their kind; and are therefore as a rational quantity to a rational one. – Encyc.