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adj. Difficult or impossible to settle by arbitration, mediation, or mutual concession: a nonnegotiable demand.

adj. Nonmarketable.

adj. Not negotiable; not subject to negotiation.

n. Something that is not negotiable.

"The second thing which I think over time, when we get past the politics and the polls, that I found I must say the most remarkable in this speech was his invocation of what he called nonnegotiable values of free speech, the nonoppression of women, religious tolerance, private property."

sine qua non   

negotiable    sociable   

reducethe    scientifical    aforementioned    unions'    insurgents'