incommensurable

adj. (often foll. By with) 1 not commensurable. 2 having no common factor, integral or fractional.  incommensurability n.

a. 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.