A conclusion or judgement; a decisive statement or declaration (expressing certainty).
現時点で彼の有罪を断定するのは早すぎる。
It's too soon to conclude that he is guilty at this point.
医師は検査結果に基づいて病名を断定した。
The doctor diagnosed the disease based on test results.
そのデータだけで結論を断定するのは危険だ。
It's dangerous to decisively conclude based on only that data.
In linguistics: 'affirmative' or the grammatical function that marks assertion/definiteness (e.g., the copula 'da' in Japanese).
日本語では断定の助動詞「だ」が文の断定を示す。
In Japanese, the copula 'da' indicates assertion/affirmation in a sentence.