Considerably; markedly; to a noticeable or significant degree.
気温が著しく下がったので暖かい服を着た。
Because the temperature dropped considerably, I wore warm clothes.
彼の成績は著しく改善した。
His grades improved markedly.
この薬は症状を著しく軽減することが報告されている。
This medicine has been reported to significantly reduce symptoms.