|in+ adjective
Etymology: Middle English, from Latin incommutabilis, from in- in- (I) + commutabilis commutable — more at commutable
: not commutable:
a. : not subject or liable to alteration : unchangeable
b. : not able to substitute one for another : unexchangeable
these incommutable skills
: not interchangeable
when two sounds are incommutable their phonetic difference prevents their being classed under one phoneme — C.E.Bazell
• in·com·mut·a·bly -blē, -bli adverb