本文探討漢語“越…越…”句與蒙古語“xedii...tödii...”句的語意與語法。兩種句式的第一個關聯詞（即第一個“越”與“xedii”）都出現在句子的主題裡，而第二個關聯詞（第二個“越”與“tödii”）則都出現在評論的部份。語意上這兩種句式都表示兩個變數之間的比例關聯；但是‘xedii...tödii...’句式還能表示兩個量的相等關係。我們主張，相等關係是比例關聯關係的一個特例。McCawley (1988)發現比例關聯句式的語意與語法跟條件句、比較句常有平行的現象。我們認為，這是由於比例關聯句式與「條件」、「比較」等概念有密切的關係。因為這種句式表示兩個變數「量」的比例關聯，一個變數的量隨著另一個變數的量而增減，語意上本來就跟「條件」有關。因為比例關聯句式牽涉到量的變化，有變化就有增有減，而所謂「增」或「減」其實就是與一個相對的「標準」比較的結果，自然與「比較」也有關係。因此，「越字句」跟「條件句」、「比較句」有類似的語法特性可以由其語意特性預測得知。

This paper aims to investigate the semantics and syntax of Mandarin 'yuè...yuè...' construction and Mongolian 'xedii...tödii...' construction. It is argued that the first yuè and xedii always occur in a topic while the second yuè and tödii appear in the comment part of a sentence. Semantically, both the 'yuè...yuè...' and the 'xedii...tödii...' constructions, the degree/quantity of y changes accordingly. The 'xedii...tödii...' construction, however, might also has a constant reading, expressing an equivalence between two fixed values on two scales. It is argued that the constant relation is a special case of the proportional correlative relation. McCawley (1988) found that the proportional constructions exhibit some syntactic properties of comparative constructions and conditional constructions. We argue that it is not a coincidence but a natural consequence. Since the degree/quantity of y depends on that of x, the construction is basically conditional. Besides, to describe the change of the degree/quantity, one must compare the degree/quantity with a standard, usually the degree/quantity at a certain point. Thus, it involves 'comparision' inherently.