mourning

mourning
n [U] black or dark clothes worn as a (conventional) sign of grief at sb's death 丧服（黑色或深色的）
    When grandmother died they went into (ie started to wear) mourning. 祖母逝世时他们开始服丧.
    She was in mourning for a month. 她服丧一个月.

牛津英汉双解词典