Fundamental; basic—relating to the root or essence of something, often implying a need for fundamental change rather than superficial fixes.
この問題は根本的な解決が必要だ。
This problem requires a fundamental solution.
その説明は根本的に間違っている。
That explanation is fundamentally wrong.
制度を根本的に見直すべきだ。
We should fundamentally review the system.