Imagine trying to speak without expressing possibility, permission,or necessity; it would be like painting without colour. That’s were the modal verb step in. These special helping verbs—can, could, ...

1 School of Foreign Languages, Huazhong University of Science and Technology, Wuhan, Hubei, China 2 Department of Chinese and Bilingual Studies, Hong Kong Polytechnic University, Kowloon, Hong Kong ...