Compromise

The verb 'to compromise' is one of those verbs ending in the sound 'EYES' (IPA: /aɪz/) for which, despite the advice in -ise - -ize, the spelling with -ise "is compulsory" (Burchfield's Fowler, s.v. -ise).

'To compromise' is derived, via the noun 'a compromise', from promise. The noun meant originally 'a mutual promise', and then 'a promise made by each of two parties to abide by the decision of an arbiter, or judge'. Thus it came to its present sense, "Adjustment for practical purposes of rival courses of action, systems, or theories, conflicting opinions or principles, by the sacrifice or surrender of a part of each" (OED). And so the basic current meaning of the verb is "To come to terms by mutual concession; to come to an agreement by the partial surrender of position or principles."

(Note that a spellchecker may allow you to - or suggest that you - substitute compromise with comprise. Both are real words, but their meanings are very different. See also comprise (grammar).)