This chapter opens the book by describing the origin and function of the copular marker “yě” (也) in the Pre-Qin period (The Pre-Qin period refers to the time before the Qin dynasty (221 BC‒206 BC) in Chinese history, consisting of the Xia, Shang, and Zhou dynasties) and its development into a focus marker, an emphasis marker, and a contrast marker. It then focuses on how the demonstrative pronoun “shì” (是), mainly as a result of analogy, became a copula. The main features of its grammaticalization are summarized: The loss of the copula “yě” and the forward movement of adverbs. It also analyzes the change in word order in interrogative sentences, arguing that Old Chinese was not an SOV type despite the wh- movement. Finally, it explores the constraints of the grammatical system on the functions of interrogative pronouns, such as universal reference, indefinite reference, and anaphora. The similarities and differences between Chinese and English are taken as an illustrative example.