youngest / most junior / tiny / one (unambiguous spoken form when spelling out numbers, esp. on telephone or in military) / one or ace on dice or dominoes / variant of 吆[yao1], to shout
Great Sage the Equal of Heaven, self-proclaimed title of the Monkey King Sun Wukong 孫悟空|孙悟空[Sun1 Wu4 kong1] in the novel Journey to the West 西遊記|西游记[Xi1 you2 Ji4]