Humans naturally acquire the language or languages that they are exposed to in early childhood, but these languages are different from one another and are all the product of historical change over many millennia, much of it resulting from chance. Natural sign languages are social creations that emerge in communities with an acute need to communicate. Many sign languages in Europe and North America developed from the establishment of schools for deaf children through the eighteenth and nineteenth centuries. The study of new sign languages such as Al-Sayyid Bedouin Sign Language (ABSL) offers a real-life view of how a language emerges a new, how it conventionalizes and spreads across users in a community. A fundamental property of human language is the existence of syntax, the level of organization that contains conventions for combining symbolic units, the words. The chapter also discusses lexicons, phonology, morphology, and semantics that characterize language.

The social situation that is built into human language includes only the communicating parties themselves, the reciprocal relations between them, and their mutual relations to an open-ended range of other possible objects to which they may attend. A related difference between language and other animal communication systems is that language allows for interaction which is much more fully dialogical. As pointed out by Benveniste, a related difference between human language and bee communication lies in the potential of language for relayed transmission of messages. This chapter describes a number of features of language and human social relations in abstract terms. It identifies a set of features which are common to all languages and which build into them a primordial social situation. The chapter exemplifies the way in which those features are used in discursive interaction, and the difference they make for triadic interaction when speech is involved.

Generative syntax embodies three complementary goals, two of which are adopted by all practitioners. The first two goals characterize what a 'possible human language' might be and provide formal grammars of individual languages. Generative syntacticians have not been very concerned with methodology. Chomsky set the tone for this lack of interest in Syntactic Structures. The generative methodology section focuses on the relative merits of introspective versus conversational data. The methodology section evaluates the recent trend to admit more and more types of semantic data as evidence in syntactic theorizing. All formal generative approaches to syntax outside of P-and-P have their roots in the lexicalist hypothesis, first proposed in Chomsky. The typological goal has in general played a much more important role in Cognitive-Functional Linguistics than in generative grammar. Cognitive-functional linguists tend to prioritize conversational and experimental data over introspective, though their day-to-day practice generally relies on the latter.

This chapter addresses structural aspects of language endangerment from two perspectives: the contributions that the study of endangered languages make to typology and linguistic theory, and the structural consequences of language endangerment, including the kinds of changes that can take place in the phonology, morphology and syntax of endangered languages. Typology is closely associated with the study of linguistic universals, which can be understood as the common characteristics of the world's languages, usually with the goal of providing insight into the fundamental nature of human language. Though there are various ways in which languages can become extinct, the most typical is through language shift when a language gradually comes to have fewer and fewer speakers who use it in ever fewer domains until finally no one is able to speak it in any context. This process is sometimes called language obsolescence.