According to these two theories, only in certain syntactic structures can a lexical item be semantically and grammatically right in a phrase, clause or sentence.
这两个理论认为，当使用于短语、从句或句子中时，词项只有在特定的句法结构中才能语义正确、合乎语法。
2
For a certain lexical item, its argument structure or valency structure determines its syntactic structure.
对词项而言，主目结构或配价结构决定句法结构。
3
'BE' is widely used in English and is related with many other syntactic rules and therefore the use of 'BE' is a very important item in grammar acquisition.