the nub of the problem/matter/argument etcMAINthe main point of a problem etc 问题/事情/争论等的焦点[要点] The real nub of the matter is money. 问题的实质是钱。
the nub of the problem/matter/argument etc• Even so, some brain cells were still working, as I stared inwardly at the nub of the problem.• It sounds perfectly reasonable, but you will perceive that here is the nub of the matter.• This is the nub of the matter.• This, however, was the nub of the problem.
→ the nub of the problem/matter/argument etc at nub(1)