In ethics, two values (or norms, reasons, or goods) are incommensurable (or incommensurate, or incomparable) when they do not share a common standard of measurement or cannot be compared to each other in a certain way.
There is a cluster of related ideas, and many philosophers use the terms differently. On one common usage:
This page is concerned almost entirely with the second phenomenon. For clarity, the term 'incomparable' is used.