taru-adjective, adverb taking the 'to' particle
Bound form used as a taru-adjective or adverb with と; mainly appears in formal or literary contexts, often in the phrase 確たる証拠 (firm evidence).
See also: 確たる証拠
As long as there is no firm evidence, we should not suspect him.
彼の主張は確とした根拠に基づいている。
His claim is based on definite grounds.
He is making that claim because he has definite grounds for it.
He firmly engraved that resolve in his heart.
確固 describes something steadfast or unshakeable (as in 確固たる意志), while 確 more broadly means 'certain/definite' and appears in phrases like 確たる証拠.
確然 is another rare literary taru-adjective meaning 'clear, distinct', which learners may confuse with 確 since both are archaic bound forms taking たる/と, but 確然 stresses visual or logical clarity rather than certainty.
The kanji 確 means 'certain' or 'firm'. The reading かく is a Sino-Japanese on'yomi, used in bound forms and compounds.
accurate; precise; exact; appropriate
conclusive evidence; positive proof; confirmation
discord; antagonism; bad blood
firm promise; definite commitment
probability variation mode (pachinko)
inaccurate; incorrect; inexact; imprecise
certain; definite; clear; credible
projected to win; sure to be elected
degree of accuracy; degree of certainty; confidence level
firm; unshakeable; resolute
detailed and accurate; meticulous; exhaustive and precise
definite report; confirmed information
profit-taking; realizing profits
validation; operation check; functionality testing
age verification
punish; confirmed counter-attack
strict adherence; steadfast defense
definite; positive; clear-cut
ascertainment; certain knowledge
definite answer; clear reply
learn from reliable sources; verify by hearing from a trustworthy source