the cardinal number that is the sum of three and one
同义词：four??/??4??/??IV??/??tetrad??/??quatern??/??quaternion??/??quaternary??/??quaternity??/??quartet??/??quadruplet??/??foursome
英汉双解词典包含3185865条英汉词条，基本涵盖了全部常用单词的翻译及用法，是英语学习的有利工具。