This paper presents＇ two equivalent definitions of the limit superior and the limit inferior for sequences of sets. The equivalences of the definitions are discussed. With examples, we show methods for finding these limits.%分析集列上（下）限集的两种定义形式，即自然语言描述形式和集合交并关系描述形式，证明它们的等价性；讨论上限集和下限集的关系，借助典型例题说明求上限集和下限集的一般方法．
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