关键词： “是……的”结构, 焦点类“是”字句, 系表类“是”字句, 判断标准

Abstract: This paper examines the determinants of Chinese cleft constructions with   是 (shi) and 的 (de).The core findings are as follows.There exist two categories of shi in the shi...de construction,with focal or predicative functions respectively.Sentences with a focal shi can be defined as cleft sentences. First, the form is "shi+S+（Ad）+V+（de）+O +（de）" or "S+shi+（Ad）+V+（de）+O+（de）".Second,shi is unstressed with no specific meaning,thus having no impact on the sentence structure once removed.In contrast to shi,de does not mark the focus of a sentence and can be omitted in many cases,and it can be placed at the end or in the middle of a sentence.Third, both shi and de are conducive in narrow the focal scale but cannot pin down the focus.The predicative shi is usually stressed in a cleft sentence,meaning "indeed" and having the attribute of a verb,hence cannot be omitted.

Key words: shi...de construction, focal shi sentences, predicative shi sentences, determinants