決め手

プログレッシブ和英中辞典(第4版)

きめて【決め手】

❶〔勝負の〕a finishing stroke; a decisive blow

あのボクサーは決め手を欠いている
That fighter lacks a KO punch.

❷〔事件などの〕a decisive [conclusive] factor；《口》 a clincher

弁護士は無罪の決め手となる証拠を提出した
His lawyer presented [introduced] decisive [conclusive/incontrovertible] proof of his innocence.

問題解決の決め手がつかめない
I can't find any key to the solution of the problem.

科学者はこの発見が癌(がん)制圧の決め手になるものと信じている
Scientists believe that this discovery will prove a great breakthrough in the fight to conquer cancer.

検事は被告を不利にする有力な決め手を欠いていた
The prosecutor could find no evidence strong enough to clinch his case against the accused.

出典　小学館「プログレッシブ和英中辞典(第4版)」