ChapterOne Introduction

1.1 Background ofthe Study

1.2 Rationale for the Study

1.3 Purpose and Method ofthe Study

1.4 Significance ofthe Study

1.5 Organization ofthe Book

Chapter Two Literature Review

2.1 Introduction

2.2 Definitions of Lexical Richness

2.3 Measures for Lexical Richness

2.4 Role ofVocabulary in L2 Writing

2.5 Developmental Features of Vocabulary in L2 Writing

2.6 Lexical Richness in Writings by L1 and L2 Learners

2.7 Lexical Richness and L2 Writing Quality

2.8 Lexical Features of L2 Writing

2.9 Research Gaps and Research Questions

2.10 Chapter Summary

Chapter Three Methodology

3.1 Introduction

3.2 Special Considerations for Research Design

3.3 Participants

3.4 Source of Data

3.5 Pilot Study

3.6 Procedures for Data Collection

3.7 Building the DIY Corpora

3.8 Data Analysis

3.9 Chapter Summary

Chapter Four Results and Findings of the Cross-sectional Study

4.1 Introduction

4.2 Features of Lexical Variation

4.3 Features of Lexical Density

4.4 Features of Lexical Sophistication

4.5 Features ofWord Length

4.6 Features of Word Frequency Distribution

4.7 Relationship between Lexical Richness and Overall Writing Performance

4.8 Chapter Summary

Chapter Five Results and Findings of the Longitudinal Study

5.1 Introduction

5.2 Features of Lexical Variation

5.3 Features of Lexical Density

5.4 Features of Lexical Sophistication

5.5 Features ofWord Length

5.6 Features of Word Frequency Distribution

5.7 Relationship between Lexical Richness and

Overall Writing Performance

5.8 Chapter Summary

Chapter Six Resultsand Findingsa cross the Two Corpora

6.1 Introduction

6.2 Patterns and Discrepancies in Lexical Variation

6.3 Patterns and Discrepancies in Lexical Density

6.4 Patterns and Discrepancies in Lexical Sophistication

6.5 Patterns and Discrepancies in Word Length

6.6 Pattems and Discrepanciesin Word Frequency Distribution

6.7 Patterns and Discrepancies in the Relationships between Lexical Richness and Overall Writing Performance

6.8 Chapter Summary

Chapter Seven Results and Findings of the Case Studies

7.1 Introduction

7.2 Results of KeynessAnalysis

7.3 Developmental Features of"we"

7.4 Developmental Features of"you"

7.5 Developmental Features of"l"

7.6 Developmental Features of"can"

7.7 Developmental Features of"know"

7.8 Developmental Features of"so"

7.9 Chapter Summary

Chapter Eight Discussion

8.1 Introduction

8.2 Overuse of High-frequency Words

8.3 Vocabulary Plateau Phenomenon in Lexical Variation

8.4 Models of Developmental Features of Lexical Richness

8.5 Unbalanced Effects of Lexical Richness on the Overall Writing Performance

8.6 The Most Overused First and Second Personal Pronouns

8.7 The Most Overused Modal Auxiliary

8.8 The Most Overused Lexical Word

8.9 The Most Overused Multi-function Word

8.10 Chapter Summary

Chapter Nine Conclusion

9.1 Summary ofthe Study

9.2 Pedagogical Implications

9.3 Limitations ofthe Study

9.4 Suggestions for Future Studies

9.5 Concluding Remarks

References

Appendix Ⅰ Prompts of WritingTask

Appendix Ⅱ Marking Scheme for TEM-4 and TEM-8 Compositions

Appendix Ⅲ Stop List

Appendix Ⅳ UCRELCLAWS7Tagset

Acknowledgements