排便是动物把体内的废物经固体或液体排出体外，即排遗。人类社会中，排便时会上厕所，又称解手、出恭、如厕。

「出恭」一词起源于明朝科举试场，考生如果需要暂时离开试场如厕，须取「出恭入敬」牌，大便称「大恭」，小便称「小恭」，因此，从语源看，「出恭」本来并不专指大便，然而在语用习惯上，「出恭」却只应用于指涉「大便」，并不指涉「小便」。《儒林外史·第十六回》：「太公日子过得称心，每日每夜出恭小解都是儿子照顾定了。」，文中把「出恭」和「小解」分述，足见两词各有分工。

「解手」为「解溲」之义。 通说「解手」起源于清朝初年的强迫性移民，湖广移民用绳子绑着，被清朝军队押送到四川。途中若要大小便，必须先向看守说声“解手”，解开绳子，后来演变为对大小便的俗称，跟「如厕」一词同样并不专指排便。

Defecation is the final act of digestion, by which organisms eliminate solid, semisolid, and/or liquid waste material from the digestive tract via the anus.

Humans expel feces with a frequency varying from a few times daily to a few times weekly. Waves of muscular contraction (known as peristalsis) in the walls of the colon move fecal matter through the digestive tract towards the rectum. Undigested food may also be expelled this way, in a process called egestion.