中文摘要：

线性电路必定满足叠加定理,满足叠加定理的电路必定是线性电路,但循环定义无助于识别线性电路和应用叠加定理。文章指出线性是线性系统输入信号与输出信号关系的一种描述,是齐次性与叠加性之和。线性电路元件是电流/电压关系特性符合线性系统输入/输出要求的电路元件,进一步可以分为自身电流与自身电压成线性关系的普通线性电路元件,和控制电压或电流与受控电压或电流成线性关系的受控线性电路元件。线性电路是由线性电路元件和独立源构成的电路,其中独立源被看做线性电路的输入（激励）,而电路中的任何电压和电流都被看做是线性电路的输出（响应）。最后根据线性概念及基尔霍夫定律,给出了叠加定理的证明。

英文摘要：

Linear circuit must meet the superposition theorem,while circuit that meets the superposition theorem must be linear circuit,but circular definition does not help in identifying linear circuits or applying superposition theorem.This article points out that linearity is a description for the input and output signal relation of linear system,which is the sum of homogeneity and additivity.Linear circuit element is any circuit element whose circuit/voltage relation meet the requirement of linear system input/output relation,which can be further divided into ordinary linear circuit element whose circuit and voltage relation of itself satisfy linearity,and controlled linear circuit element whose controlled signal and control signal relation satisfy linearity.Linear circuit is composed by linear element and independent source wherein independent source is seen as input（excitation） of linear circuit while any voltage and circuit are seen as output（response）.Finally a proof is given based on the concept of linearity and Kirchhoff＇s Law.