The document defines language and its key components and features. It discusses language as a tool for communication that can be analyzed based on its communicative, structural, and interactional aspects. The structures of language include specific languages as well as the underlying design plan common across languages. All languages have sound systems, words, and grammar. Style is a variation in language that reflects social identities and can be classified based on levels of formality from frozen to intimate. Factors like occasion, social class, education, age, gender, and ethnicity can influence one's language style.