A kowtow is the act of deep respect shown by prostration, that is, kneeling and bowing so low as to have one's head touching the ground. In Sinospheric culture, the kowtow is the highest sign of reverence. It was widely used to show reverence for one's elders, superiors, and especially the Emperor of China, as well as for religious and cultural objects of worship. In modern times, usage of the kowtow has been reduced.
