本文考察了“合该”自宋代出现以来词义和用法发展演变的过程,探讨了它逐渐衰落的动因。宋元时期“合该”多用于史书、政府文书、科技文书等书面正式语体,表示经过计算或核准后所得出的结论,或符合客观事实、社会规约、法律规定的事态发展趋势或结果,相当于“应该”“理应”。明清时期,“合该”大量出现在小说中,主观性增强,至迟从明代开始基本可以认定为语气副词。其在现代汉语中的衰落应该是受“应该”“活该”排挤的结果。 This paper examines the process of the evolution and development of meaning and usage since the emergence of the Song Dynasty in Song Dynasty and explores the motivation for its gradual decline. During the Song and Yuan dynasties, “合” was mostly used in written official style such as history books, government documents, scientific documents and so on, indicating that after calculation or approval, the conclusions reached afterwards or in line with objective facts, social norms, The result is equivalent to “should ” “reason”. In the Ming and Qing Dynasties, “together ” appeared in a large number of novels, subjectivity increased, from the beginning of the Ming Dynasty can be identified as the basic modal adverbs. Its decline in modern Chinese should be the result of crowding out by “” should “” deserve ".