To feel sadness or sorrow; to grieve, mourn, or regret (something). Often used for mourning losses or expressing emotional pain.
彼は母の死を深く悲しんでいる。
He is deeply mourning his mother's death.
試験に落ちて、しばらくの間彼女は悲しんでいた。
She was sad for a while after failing the exam.
大切な試合に負けて、チーム全員が悲しんだ。
The whole team was saddened after losing the important match.