необходимый(necessary; that cannot be done without • A dictionary should be considered an indispensable possession); обязательный(о законе и т. п.); не допускающий исключений; неотъемлемый; совершенно необходимый; непременный; незаменимый(Not too often, mind you – no point in giving a man the sense that he was indispensable.); то, без чего невозможно обойтись(Brennan, of course, is President Obama's highly-trusted national security and counterterrorism advisor, the co-architect and co-executor, with Obama, of the expanded, worldwide drone assassination policy – so trusted that The New York Times has described him as "a priest whose blessing has become indispensable to Mr. Obama, echoing the president's attempt to apply the 'just war' theories of Christian philosophers to a brutal modern conflict.thepolemicist.net); нужный
thepolemicist.net); нужный