And you don't get a complete straight line but you get an interesting function that suggest that there's a relationship.

你不会得到一条完整的直线,但会得到一个有趣的函数,表明他们之间的某种关系

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In the meantime, what Saussure is doing with this relationship above and below the line is, he is saying that there is an arbitrary relationship between the concept and the sound image.

同时，索绪尔觉得这组关系,也就是线上和线下的这个组合，他说，这是一个任意的组合,在事物和声音形象之间。

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