α1,α2,⋯ ,αr\alpha_{1},\alpha_{2},\cdots,\alpha_{r}α1,α2,⋯,αr及α1,α2,⋯ ,αr,⋯ ,αs(其中s≥r)\alpha_{1},\alpha_{2},\cdots,\alpha_{r},\cdots,\alpha_{s}(其中s\geq r)α1,α2,⋯,αr,⋯,αs(其中s≥r),称α1,α2,⋯ ,αr\alpha_{1},\alpha_{2},\cdots,\alpha_{r}α1,α2,⋯,αr是α1,α2,⋯