Language is the
human capacity for acquiring and using complex systems of
communication, and
a language is any specific example of such a system. The scientific study of language is called
linguistics.
Estimates of the number of languages in the world vary between 6,000 and 7,000. However, any precise estimate depends on a partly arbitrary distinction between languages and
dialects.
Natural languages are
spoken or
signed, but any language can be
encoded into secondary media using auditory, visual, or tactile
stimuli, for example, in
graphic writing,
braille, or
whistling. This is because human language is modality-independent. When used as a general concept, "language" may refer to the
cognitive ability to learn and use systems of complex communication, or to describe the set of rules that makes up these systems, or the set of utterances that can be produced from those rules. All languages rely on the process of
semiosis to relate
signs with particular
meanings.
Oral and
sign languages contain a
phonological system that governs how symbols are used to form sequences known as words or
morphemes, and a
syntactic system that governs how words and
morphemes are combined to form phrases and utterances.
Human language is unique because it has the properties of
productivity,
recursivity, and
displacement, and because it relies entirely on social convention and learning. Its complex structure therefore affords a much wider range of possible expressions and uses than any known system of
animal communication. Language is thought to have originated when early
hominins started gradually changing their primate communication systems, acquiring the ability to form a
theory of other minds and a shared
intentionality.
This development is sometimes thought to have coincided with an increase in brain volume, and many linguists see the structures of language as having evolved to serve specific communicative and social functions. Language is processed in many different locations in the
human brain, but especially in
Broca's and
Wernicke's areas. Humans
acquire language through social interaction in early childhood, and children generally speak fluently when they are approximately three years old. The use of language is deeply entrenched in human
culture. Therefore, in addition to its strictly communicative uses, language also has many social and cultural uses, such as signifying group
identity,
social stratification, as well as for
social grooming and
entertainment.
Languages
evolve and diversify over time, and the history of their evolution can be reconstructed by
comparing modern languages to determine which traits their ancestral languages must have had in order for the later stages to have occurred. A group of languages that descend from a common ancestor is known as a
language family. The languages that are most spoken in the world today belong to the
Indo-European family, which includes languages such as
English,
Spanish,
Portuguese,
Russian, and
Hindi; the
Sino-Tibetan languages, which include
Mandarin Chinese,
Cantonese, and many others;
Semitic languages, which include
Arabic,
Amharic, and
Hebrew; and the
Bantu languages, which include
Swahili,
Zulu,
Shona, and hundreds of other languages spoken throughout
Africa. The consensus is that between 50 and 90% of languages spoken today will probably have become extinct by the year 2100.