392. A language is a signaling system which operates with symbolic vocal sounds, and which is used by a group of people for the purpose of communication.

英语四级译文:
语言就是通过象征性语声起作用，并为了沟通的目的而被一群人使用的信号系统。

四级词汇讲解:
两个which引导的都是system的定语从句。operate with意为“借助……运转”。

for the purpose of意为“出于……的目的”。如:
This book is for the purpose of studying the very subject.该书正是为研究此学科而写成的。

英语四级考点归纳:
有关purpose的常见短语有:

※ on purpose意为“并非偶然地，故意地”。如:
They seemed to do those things on purpose.他们似乎是有意做那些事的。

※ serve one's/the purpose意为“适合需要;令人满意”。如:
The plan will serve your purpose.该计划会令你满意。

※ to little/no/some purpose意为“几乎没有/毫无/有一定成效”。如:
Money has been invested in the scheme to little purpose.资金已投入到该方案之中，却几乎毫无成效。