プログレッシブ和英中辞典(第4版)の解説
かく【欠く】
❶〔損なう〕break；〔一部を壊す〕chip
皿を欠く
chip a dish
刃物を欠く
chip the blade of a knife／〔先端を〕break (off) the tip of a knife
転んで前歯を欠いた
I fell down and broke a front tooth.
氷を小さく欠く
chip ice
❷〔あるべきものがない〕lack
礼儀を欠く
lack good manners
勇気を欠く
lack [《文》 be wanting in] courage
義理を欠く
fail to carry out one's duty [obligations]
あれは常識を欠く行動だった
His conduct was not entirely proper.
彼の仕業だと断定するには決め手を欠く
We have no conclusive evidence to prove that he did it.
全集の第３巻を欠く
The third volume of the set is missing.
欠くべからざる
成功に欠くべからざる条件
conditions 「absolutely necessary [indispensable/essential] to [for] success