This question already has an answer here:

Some scientific domains use additional units that are not part of the SI system and not generally used at all, for example:

The z-ness was increased by 5 Z, resulting in a xyability of 7 Xy/second.

Is it possible to use such "phantasy" units together with the siunitx package? (Instead of special treatment of all cases that involve such an unit.)

marked as duplicate by Mico, TeXnician, Harald Hanche-Olsen, Zarko, user36296 Jun 5 '18 at 8:29

This question has been asked before and already has an answer. If those answers do not fully address your question, please ask a new question.

Browse other questions tagged or ask your own question.