There are many definitions of art, few of which make much sense to the uninitiated.

艺术有多种定义，外行人一般都难以理解。

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The introduction talks about the significance of research topic, state of the art, origin of reference and relevant definitions.

绪论部分交待了选题的意义、研究现状、资料来源和对相关概念的界定。

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In essence, with the AIA, Congress has enacted a definition of prior art that will slowly displace the old definitions, but it may take decades for the new legislation to fully displace the old definitions of prior art.

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