threeleaf三叶threenum.三n.三；三个adj.三个的three scoops of flour三杓子面粉three-colour system三色系统three leg transformer三腿铁芯变压器three-phase exciter三相励磁机,三相激磁器three primary colours三原色three-level network三级网络Three-knife trimmer三面切书机Three-circle Theory三圈理three line relaxation三线放松法three o'clock welding