the cardinal number that is the sum of three and one
同义词：four, 4, IV, tetrad, quatern, quaternion, quaternary, quaternity, quartet, foursome, Little Joe
one of four children born at the same time from the same pregnancy
同义词：quad
a set of four similar things considered as a unit
同义词：quartet, quartette, quadruple
quadruplet详细解释
quad.ru.plet
n.（名词） One of four offspring born in a single birth. 四胞胎之一：一胎出生的四个孩子中的一个 A group or combination of four associated by common properties or behavior. 四个构成的一组：因共同的财产或行为而联系在一起的四人小组或联盟
