threestepadj.三级的threenum.三n.三；三个adj.三个的three-terminal element三端元件three-dimensional wall三维墙Three-banded Rosefinchn.斑翅朱雀Three Frame Differencing三帧差three-tiered structure三层体系three room and two halls三室两厅three-wattmeter method三瓦特计法three bench construction三台阶施工Three-level structures三级构造three carbon tautomerism[化] 三碳互变异构现象