悲しむ
かなしむ · kanashimu · JLPT N3 · verb-godan
to be sad
🥀 悲しい (sad) minus い plus む = to be sad; 悲 = 非 wrong + 心 heart
悲しむ is the verb form of the adjective 悲しい (kanashii, sad): drop the い and add the verb ending む. The kanji 悲 puts 非 (wrong, against) on top of 心 (heart), so it reads as a heart gone wrong.