Foolish or stupid; lacking good judgment or wisdom, often leading to poor results (na-adjective).
そんな愚かな行為は二度と繰り返してはいけない。
You must never repeat such a foolish act again.
彼の決定は愚かだと多くの人が批判した。
Many people criticized his decision as foolish.
愚かと言われても、自分の信念を曲げるつもりはない。
Even if I'm called foolish, I don't intend to abandon my convictions.
愚かな過ちから学ぶことが大切だ。
It's important to learn from foolish mistakes.