孝 is a bound form (b.f.) that embodies the Confucian virtue of filial piety — respect, obedience, and care for one's parents, as well as mourning duties after a parent's death. It appears as a morpheme in compounds such as 孝顺 (xiàoshùn, 'filial'), 孝敬 (xiàojìng, 'to show filial respect'), and 尽孝 (jìn xiào, 'to fulfill filial obligations'). The mourning sense refers to the traditional requirement for children to observe a period of mourning, including wearing mourning dress.