Abstract: Rhetorical modal adverbs are a special kind in both Chinese and Korean languages. They have flexible syntactic positions and empty sematic meanings. Therefore, they are one of the difficulties in teaching Chinese as a foreign language and Korean language. Taking Chinese and Korean students as the research object, this paper makes a questionnaire survey on the use of Chinese and Korean rhetorical modal adverbs, and analyses the errors of Chinese and Korean rhetorical modal adverbs from the perspective of syntax and semantics. The syntactic distribution errors include the wrong ordering at the beginning and middle of the sentence. The syntactic combination errors include the misuse of modal particles and auxiliary verbs. The semantic errors include the misunderstanding of rhetorical meaning and the misunderstanding of realistic and non-realistic meaning. Among these, the error rate of syntactic combination is the highest. This is because the differences between Chinese and Korean are reflected most in the combination characteristics of rhetorical modal adverbs. Students are influenced by their mother tongue and have many errors. This part is the key and difficult point in the teaching of rhetorical modal adverbs. It is necessary to carry out targeted teaching for individual rhetorical modal adverbs with high error rate.

Universal grammar has exerted meaningful influence on the development of second language acquisition theories. SLA researchers working within UG have addressed the question whether second language developments are constrained by universal language principles. This paper reviews current developments in UG-based SLA research with a view to providing a better understanding of the role of UG principles in foreign language sentence structure development.