Their relationship is necessary but, as we'll see in a minute, arbitrary, and each sign is like that.

这种关系十分必要，但是它又有任意性。

耶鲁公开课 - 文学理论导论课程节选

So that what's new in Saussure's thinking about the relationship between signified and signifier is that the sign tied up in this relationship is both arbitrary and differential.

这就是索绪尔所贡献的了,能指和所指的关系,也就是符号的组成方式,是任意的，有差别的。

耶鲁公开课 - 文学理论导论课程节选