This is a textbook on linguistic theory for undergraduate students majoring in Chinese Language and Literature or TCFL (Teaching Chinese as a Foreign Language). It can also be used by postgraduate Linguistics and Applied Linguistics majors. This book, 10 chapters in all, gives a comprehensive summarization on the nature and function of language as well as the basic concepts and theory on linguistics, such as the language structure and system, phonology, semantics, grammar and pragmatics. It also explains the ABC of Cross-Linguistic disciplines, such as Sociolinguistics, Psycholinguistics, Cognitive Linguistics, Computational Linguistics and Applied Linguistics. Meanwhile, it makes a brief discussion and analysis on language development.