| English Abstract | 第4页 |
| Chinese Abstract | 第5-8页 |
| Introduction | 第8-9页 |
| Chapter 1. A Review of Prototype Theory | 第9-14页 |
| 1.1 An introduction to prototype theory | 第9-10页 |
| 1.2 Prototype view on categorization | 第10-13页 |
| 1.2.1. boundary fuzziness | 第11-12页 |
| 1.2.2. category overlapping | 第12页 |
| 1.2.3. necessary and sufficient features | 第12-13页 |
| 1.3 Attributes of prototype theory | 第13页 |
| 1.4 The advantages of prototype theory | 第13-14页 |
| Chapter 2. Instability of the Prototype Graded Structures | 第14-23页 |
| 2.1 Changing of the prototypical structures | 第15-20页 |
| 2.2 The influence of unstable prototype structures on categorization | 第20-23页 |
| Chapter 3. Implications of Prototype Theory in Language Acquisition | 第23-28页 |
| 3.1 Prototypicality effects | 第23-24页 |
| 3.2 Prototype and memory keeping time | 第24-25页 |
| 3.3 A hint from the case of “go”related to tense | 第25-27页 |
| 3.4 Maximum of the information with the least cognitive effort | 第27页 |
| 3.5 Prototype focus attention on the relationship between words and things | 第27页 |
| 3.6 Gaps in learner’s understanding of the prototype items | 第27-28页 |
| Chapter 4. Grammatical Categorization of Modal Auxiliaries | 第28-37页 |
| 4.1 Prototype nature of linguistic categories | 第28页 |
| 4.2 Graded structure of modal auxiliaries | 第28-29页 |
| 4.3 Impreciseness and category membership | 第29-31页 |
| 4.4 Centrality of features | 第31-32页 |
| 4.5 Multiple foci | 第32-35页 |
| 4.5.1. the permission / possibility / ability modals | 第33-34页 |
| 4.5.2. the obligation / necessity modals and semi-modals | 第34页 |
| 4.5.3. the volition / prediction modals and semi-modals | 第34-35页 |
| 4.6 Teaching principles for enumerating | 第35-37页 |
| Conclusion | 第37-38页 |
| References | 第38-39页 |
| Acknowledgements | 第39页 |
