Better naming and variants

[LLyaudet]

I chose a word half-latin, half-greek with ratio-delta, kind of reverse of hexadecimal. I do not claim this is the best possible word. I only claim that at least for communicating between humans, it deserves a word to be precise and avoids ambiguity. The word I chose composes easily with absolute, percent, and rounded. Moreover, it is not too long (I thought about shrinking it into "relta" but there is already a repository with that name on GitHub.). If you have better ideas, please share it with us here :)