〈疑いのない〉 undoubted; unquestionable; 【形式ばった表現】 indubitable
〈疑いなく〉 no doubt; undoubtedly; beyond [without] doubt; decidedly; 【形式ばった表現】 indubitably
確か(なもの)にする
〈信頼すべき〉 reliable; trustworthy
確か(なもの)にする
〈立証する〉 confirm; verify; 【形式ばった表現】 corroborate; 【形式ばった表現】 substantiate
have 《the news》 on good authority
〈確実に〉 certainly; surely; for certain; to be sure; definitely
〈誓って〉 upon one's word [honor]
yes [no]
読み方 たしか
(=確実な) certain (fact); sure(way); assured (fact); positive (proof); authentic (news); secure (possession); safe (plan); true (aim); genuine (article); conclusive (evidence); convincing (proof); decisive (proof); definite (answer); reliable (source); trustworthy (quarter); sound (doctrine); solid (grounds); firm (basis); steadfast (friend); established (fact); competent (teacher); good, gilt-edged (security, etc.)
1
(=に)(=確実に) certainly; to a certainty; of a certainty; of a surety; as sure as I am alive; as sure as eggs is eggs; as sure as a gun; as sure as death; as sure as you are there
2
(=多分) I think; I believe; if I am not mistaken; if I remember aright