incommensurable

Concise Oxford English Dictionary © 2008 Oxford University Press:
incommensurable /ˌɪnkəˈmɛnʃ(ə)rəb(ə)l, -sjə-/

▶adjective

• 1 not able to be judged or measured by the same standards; having no common standard.

• 2 Mathematics (of numbers) in a ratio that cannot be expressed as a ratio of integers.

▶noun an incommensurable quantity.

– derivatives
incommensurability noun,
incommensurably adverb.