本文总结并提出了较为完备的特征提取定义。根据特征子集形成过程将特征选择分为穷举式、启发式和随机式三类 根据特征评价标准将特征选择分为距离浏度、信息测度、相关性浏度、一致性测度和分类器错误率五类。通过分析特征选择的影响因素，提出了选择特征、选择方法应该遵循的原则。

-This paper analyzes and summarizes the previous definition of feature selection, and then introduces a selfcontained definition. It divides feature selection into three classes according to the selecting strategy, and categorizes the methods into five styles by the evaluation function. Through analyzing the infection factors in the feature selection technology,this paper introduces some principles to pave the way for practitioners who search for suitable features to solve realworld applications.