服丧

Confucian funerary rites prescribed an elaborate mourning system codified in 《礼记》: a son was expected to 服丧 for three years (in practice 27 months) after a parent's death, wearing coarse hemp garments (麻衣) and abstaining from feasts, music, and official duties. The system shaped Chinese family politics for two millennia - emperors had to retire from court during 守孝 (shǒuxiào).

Formal/written register. In modern speech 守孝 (shǒuxiào, 'observe filial mourning') is more common for the same idea. Note the pinyin: 丧 here is sāng (1st tone) meaning 'funeral/mourning', not 丧 sàng (4th tone) 'to lose'.