| Lexical richness is an important quantitative index for evaluating the vocabulary level of L2 learners,which can effectively measure the depth and breadth of vocabulary learning.Therefore,the study of lexical richness has received extensive attention and has become a hot spot in the study of L2 vocabulary acquisition.At present,most of the related research focuses on the field of English as a second language acquisition.Although some researchers have paid attention to the research on lexical richness of Chinese learners,most of them focus on one or several dimensions.In addition,many relevant studies are horizontal research,ignoring the dynamic changes of lexical systems development.The only few longitudinal studies are mostly short-term studies within two months or one semester,making it difficult to find different stages of vocabulary development and turning points in the development.Therefore,based on the lexical richness theory of Read（2000）,this study investigates the development of lexical richness among Malaysian students.From the perspective of horizontal research,learners of different grades are measured in terms of lexical density,lexical variation,lexical sophistication and lexical errors to examine their differences in lexical richness,and the key points of each dimension development path are combined with the corresponding texts,to provide a realistic basis for the results of quantitative analysis.From the perspective of longitudinal research,we have investigated the dynamic development path of three learners over six semesters,to identify the key points of vocabulary development.The results of horizontal study show that:Firstly,among the four measurement dimensions,lexical density cannot effectively examine the quality and richness of word expression.Secondly,the increase in grade level is generally accompanied by an upward trend in lexical variation and lexical sophistication.However,this is an exception in the third grade,where development slows down or even regresses.The writing texts of the four grades show three progressive levels in terms of word expression.Thirdly,the rate of lexical errors decreases significantly with the increasing grade.Among these errors,usage errors and formal errors decrease significantly,while semantic errors gradually increase.Finally,the rank distribution of incorrect words shows a significant change in the learners’tendency to use complex words.The longitudinal research results show that:The vocabulary development path of the three learners shows non-linear development characteristics of jumping and fluctuating.Although the vocabulary development path of the three learners is not exactly the same,they show great similarity and regularity.To put it another way,they all undergo three different development stages in the development process.Furthermore,it was found that the development of learners’ vocabulary ability is usually accompanied by the change of social-stylistic features. |
