∑+=Σ-{e}=∑Σ=∑∪22∪Σ3∪ 区区{3}=区 例:Σ={a,b} ∑*={ε,a,b,aa,ab,ba,bb,aaa,ab, 2+=a, b aa, ab, ba, bb, aaa, aab,...例：Σ={a,b} Σ*={ε,a,b,aa,ab,ba,bb,aaa,aab,…} Σ+={a,b,aa,ab,ba,bb,aaa,aab,…} ...... } { 2 *      =  { } ...... * * 2 3  =  − =  =    + 