As the chief function of functional words is to express the rela

As the chief function of functional words is to express the relation between notions, the relation between words as well as sentences, they are known as ( ) words.
【正确答案】：FORM
【题目解析】：本题考查虚词的含义。功能词本身不具有实义，也称为虚词。虚词就是表示两个实义词之间以及词与词，句子与句子之间的关系，也可称为形式词。比如：介词、连词、助动词、冠词。form：形式。