on second thought; come to think of it; actually
Used when reconsidering or realizing something after a moment of thought, often introducing a changed opinion or a new insight.
Come to think of it, he might be right.
On second thought, today was a day off.
Kanji spelling for よく; less common but seen in formal writing.
Phrase composed of よく (well, carefully) + 考えたら (conditional form of 考える, 'to think'). Literally 'if one thinks carefully'.