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Chapter Two   Literature Review 

Vocabulary can be seen as the basic bricks if a language system is treated as a tall building.  It  is  the  beginning  of  learning  a  second  language,  and  it  runs  through  the whole process of second language acquisition. No language ability can be learned or developed without vocabulary. As one of the four basic skills, writing is an important area in second language learning. It needs the support of grammar, vocabulary and the culture knowledge of the target language, especially the vocabulary. (Luan Lan，2013) Ever  since  the  1980s,  more  and  more  researchers  and  practitioners  in  the  areas  of second  language  acquisition  and  language  teaching  began  to  pay  attention  to  the studies  on  vocabulary  in  second  language  writing.  The  previous  studies  can  be broadly divided into two kinds. One kind mainly deals with width of vocabulary and the other kind mainly focuses on depth of vocabulary. From the first kind of studies, second language learners’ width of vocabulary mainly refers to lexical richness which is  considered  as  an  important  indicator  of  second  language  writing  proficiency.    Many researchers think lexical richness is a predicator of a language leaner’s overall language proficiency, and it is also an important indicator of the quality of a learner’s writing  and  communication.  (e.g.  Laufer  &  Nation,  1995;  O’Loughlin,  1995;  Javis, 2002)  The  literature  review  part  will  give  definitions  of  some  important  theoretical concepts and review those studies of previous scholars at home and abroad.  

2.1   Definitions of Lexical Richness 
Lexical richness has been treated as a prominent predicator of language learners’ general  language  proficiency  (Zareva  et  al.,  2005)  and  an  essential  indicator  of  the quality  of  their  writings.  (Laufer  &  Nation,  1995)  There  is  no  definition  that  can  be accepted by all the researchers. In the past years, with the development of the studies in  this  area,  different  meanings  have  been  added  to  this  notion.  Some  researchers defined  lexical  richness  as  an  equivalent  to  lexical  diversity  and  lexical  complexity. (Daller  et  al,  2003;  Laufer,  1991;  Read,  2000;  Wolfe-Quintero  et  al,  1998)  In  the meantime,  some  researchers  defined  lexical  richness  as  something  different  from lexical  diversity  which  is  considered  as  one  part  of  the  multidimensional  features  of lexical richness. (Malvern et al., 2004) Engber 本论文由英语论文网提供整理，提供论文代写，英语论文代写，代写论文，代写英语论文，代写留学生论文，代写英文论文，留学生论文代写相关核心关键词搜索。