three plyadj.三层的(三股的；三夹板)threenum.三n.三；三个adj.三个的three-through pump三联泵three big components三大构成three-index symbol三索引符号,三下标符号three tins of coffee三听咖啡three-leg inverter三桥臂逆变器three -tank system三容水箱three-view drawing三面图three-axle trailer三轴挂车three-color theory三原色论three-hole element三孔元件