nub

n [sing] the ~ of sth central or essential point of a problem, matter, etc （问题、 事情等的）中心,要点: The nub of the problem is our poor export performance. 问题的关键是我们出口贸易方面太差.

novelist, novelty, November, novice, noviciate (also novitiate), now, now and then, now that, nowadays, nowhere, noxious, noxiously, noxiousness, nozzle, nr, NSB, NSPCC, NT, nth, nuance, nubile, nuclear, nuclear disarmament, nuclear energy (also nuclear power), nuclear family, nuclear war, nuclear winter, nuclear-free, nucleate, nucleic acid, nucleolus, nucleus, nude, nudge, nudism, nudist, nudist camp (also nudist colony), nudity, nugatory, nugget,