A group of languages that descend from a common ancestor is known as a language family. The Indo-European family is the most widely spoken and includes English, Spanish, Portuguese, Russian, and Hindi; the Sino-Tibetan family, which includes Mandarin Chinese, Cantonese, and many others; the Afro-Asiatic family, which includes Arabic, Amharic, Somali, and Hebrew; the Bantu languages, which include Swahili, Zulu, Shona, and hundreds of other languages spoken throughout Africa; and the Malayo-Polynesian languages, which include Indonesian, Malay, Tagalog, Malagasy, and hundreds of other languages spoken throughout the Pacific. The languages of the Dravidian family that are spoken mostly in Southern India include Tamil, Telugu, Kannada and Malayalam. Academic consensus holds that between 50% and 90% of languages spoken at the beginning of the twenty- first century will probably have become extinct by the year 2100.
Yet another definition sees language as a system of communication that enables humans to exchange verbal or symbolic utterances. This definition stresses the social functions of language and the fact that humans use it to express themselves and to manipulate objects in their environment. Functional theories of grammar explain grammatical structures by their communicative functions, and understand the grammatical structures of language to be the result of an adaptive process by which grammar was "tailored" to serve the communicative needs of its users.
This view of language is associated with the study of language in pragmatic, cognitive, and interactive frameworks, as well as in sociolinguistics and linguistic anthropology. Functionalist theories tend to study grammar as dynamic phenomena, as structures that are always in the process of changing as they are employed by their speakers. This view places importance on the study of linguistic typology, or the classification of languages according to structural features, as it can be shown that processes of grammaticalization tend to follow trajectories that are partly dependent on typology.
