Natural language
{{Neuropsychology}}
In the [[philosophy of language]], a '''natural language''' (or '''ordinary language''') is a [[language]] that is spoken, [[writing|written]], or [[Sign language|signed]] by [[animal]]s for general-purpose communication, as distinguished from  [[formal language]]s  (such as [[Programming language|computer-programming languages]] or the "languages" used in the study of formal [[logic]], especially [[mathematical logic]]) and from [[constructed language]]s.

== Defining natural language ==

Though the exact definition is debatable, natural language is often contrasted with artificial or [[constructed languages]] such as [[Esperanto]], [[Latino Sexione]], and [[Occidental language|Occidental]].

Linguists have an incomplete understanding of all aspects of the rules underlying natural languages, and these rules are therefore objects of study.  The understanding of natural languages reveals much about not only how language works (in terms of [[syntax]], [[semantics]], [[phonetics]], [[phonology]], etc), but also about how the human [[mind]] and the human [[brain]] process language.  In linguistic terms, 'natural language' only applies to a language that has evolved naturally, and the study of natural language primarily involves native (first language) speakers.  

The theory of [[universal grammar]] proposes that all natural languages have certain underlying rules which constrain the structure of the specific grammar for any given language.

While [[grammarians]], writers of dictionaries, and language policy-makers all have a certain influence on the evolution of language, their ability to influence what people think they 'ought' to say is distinct from what people actually say. Natural language applies to the latter, and is thus a 'descriptive' rather than a 'prescriptive' term.  Thus non-standard language varieties (such as [[African American Vernacular English]]) are considered to be natural while standard language varieties (such as [[Standard American English]]) which are more 'prescripted' can be considered to be at least somewhat artificial or constructed.

== Native language learning ==
{{main|Language acquisition}}
The [[learning]] of one's own [[native language]], typically that of one's [[parent]]s, normally occurs spontaneously in early human [[childhood]] and is [[Biology|biologically]] driven.  A crucial role of this process is performed by the [[Nervous system|neural]] activity of a portion of the human [[brain]] known as [[Broca's area]].

There are approximately 7,000 current human languages, and many, if not most seem to share certain properties, leading to the belief in the existence of [[Universal Grammar]], as shown by [[generative grammar]] studies pioneered by the work of [[Noam Chomsky]].  Recently, it has been demonstrated that a dedicated network in the human brain (crucially involving [[Broca's area]], a portion of the left inferior frontal gyrus), is selectively activated by complex verbal structures (but not simple ones) of those languages that meet the Universal Grammar requirements.<ref>A. Moro, M. Tettamanti, D. Perani, C. Donati, S. F. Cappa, F. Fazio “Syntax and the brain: disentangling grammar by selective anomalies”, NeuroImage, 13, January 2001, Academic Press, Chicago, pp. 110-118</ref> <ref> Musso, M., Moro, A. , Glauche. V., Rijntjes, M., Reichenbach, J., Büchel, C., Weiller, C. “Broca’s area and the language instinct,”  Nature neuroscience, 2003, vol. 6, pp. 774-781.</ref>

== Origins of natural language ==
{{main|Origin of language}}

There is disagreement among anthropologists on when language was first used by humans (or their ancestors).  Estimates range from about two million (2,000,000) years ago, during the time of ''[[Homo habilis]]'', to as recently as forty thousand (40,000) years ago, during the time of [[Cro-Magnon]] man. However recent evidence suggests modern human language was invented or evolved in Africa prior to the dispersal of humans from Africa around 50,000 years ago. Since all people including the most isolated indigenous groups such as the [[Andamanese]] or the [[Tasmanian aboriginals]] possess language, then it must have been present in the ancestral populations in Africa before the human population split into various groups to colonize the rest of the world. <ref>[http://query.nytimes.com/gst/fullpage.html?res=9503E0DF173CF936A25754C0A9659C8B63&sec=health&spon=&pagewanted=1  Early Voices: The Leap to Language nytimes article by] [[Nicholas Wade]]</ref> <ref>[http://www.arthist.lu.se/kultsem/pro/SverkerJohansson-sem.pdf Origins of language constraints on hypotheses]
</ref>

Some claim that all nautural languages came out of one single language, known as [[Adamic]].

== Linguistic diversity ==
{{see also|Multilingualism}}
As of early 2007, there are 6,912 known living human languages. <ref>[http://www.ethnologue.com/ "Ethnologue: Languages of the World, Fifteenth edition"], accessed [[28 June]] [[2007]], ISBN 1 55671 159 X</ref>  A "living language" is simply one which is in wide use by a specific group of living people.  The exact number of known living languages will vary from 5,000 to 10,000, depending generally on the precision of one's definition of "language", and in particular on how one classifies [[dialects]].  There are also many dead or [[extinct language]]s.

There is no [[dialect#.22Dialect.22 or .22language.22|clear distinction]] between a language and a [[dialect]], notwithstanding linguist [[Max Weinreich]]'s famous [[aphorism]] that "[[a language is a dialect with an army and navy]]." In other words, the distinction may hinge on political considerations as much as on cultural differences, distinctive [[writing system]]s, or degree of [[mutual intelligibility]].

It is probably impossible to accurately enumerate the living languages because our worldwide knowledge is incomplete, and it is a "moving target", as explained in greater detail by the [[Ethnologue]]'s Introduction, p. 7 - 8.  With the 15th edition, the 103 newly added languages are not new but reclassified due to refinements in the definition of language.

Although widely considered an [[encyclopedia]], the [[Ethnologue]] actually presents itself as an incomplete catalog, including only named languages that its editors are able to document.  With each edition, the number of catalogued languages has grown.  

Beginning with the 14th edition (2000), an attempt was made to include all known living languages.  SIL used an internal 3-letter code fashioned after [[airport code]]s to identify languages.  This was the precursor to the modern [[ISO 639-3]] standard, to which SIL contributed.  The standard allows for over 14,000 languages.  In turn, the 15th edition was revised to conform to the pending ISO 639-3 standard.

Of the catalogued languages, 497 have been flagged as "nearly extinct" due to trends in their usage.

Per the 15th edition, 6,912 living languages are shared by over 5.7 billion speakers. (p. 15)

== Taxonomy ==

The [[Taxonomic classification|classification]] of natural languages can be performed on the basis of different underlying principles (different closeness notions, respecting different properties and relations between languages); important directions of present classifications are: 
* paying attention to the historical evolution of languages results in a genetic classification of languages&mdash;which is based on genetic relatedness of languages,
* paying attention to the internal structure of languages ([[grammar]]) results in a typological classification of languages&mdash;which is based on similarity of one or more components of the language's grammar across languages,
* and respecting geographical closeness and contacts between language-speaking communities results in areal groupings of languages.

The different classifications do not match each other and are not expected to, but the correlation between them is an important point for many [[linguistics|linguistic]] research works. (There is a parallel to the classification of [[species]] in biological [[phylogenetics]] here: consider [[monophyletic]] vs. [[polyphyletic]] groups of species.)

The task of genetic classification belongs to the field of [[historical-comparative linguistics]], of typological&mdash;to [[linguistic typology]].

See also [[Taxonomy]], and [[Taxonomic classification]] for the general idea of classification and taxonomies.

==== Genetic classification ====
{{main|Language family}}

The world's languages have been grouped into families of languages that are believed to have common ancestors. Some of the major families are the [[Indo-European languages]], the [[Afro-Asiatic languages]], the [[Austronesian languages]], and the [[Sino-Tibetan languages]].

The shared features of languages from one family can be due to shared ancestry. (Compare with [[homology (biology)|homology]] in biology.)

==== Typological classification ====
{{main|Linguistic typology}}

An example of a typological classification is the classification of languages on the basis of the basic order of the [[verb]], the [[subject (grammar)|subject]] and the [[object (grammar)|object]] in a [[sentence (linguistics)|sentence]] into several types: [[SVO language|SVO]], [[SOV language|SOV]], [[VSO language|VSO]], and so on, languages. ([[English language|English]], for instance, belongs to the [[SVO language]] type.)

The shared features of languages of one type (= from one typological class) may have arisen completely independently. (Compare with [[analogy (biology)|analogy]] in biology.) Their cooccurence might be due to the universal laws governing the structure of natural languages&mdash;[[language universal]]s.

==== Areal classification ====
{{main|Areal feature}}
The following language groupings can serve as some linguistically significant examples of areal linguistic units, or ''[[sprachbund]]s'': [[Balkan linguistic union]], or the bigger group of [[European languages]]; [[Caucasian languages]]; [[East Asian languages]]. Although the members of each group are not closely [[genetic relatedness of languages|genetically related]], there is a reason for them to share similar features, namely: their speakers have been in contact for a long time within a common community and the languages ''converged'' in the course of the history. These are called "[[areal feature (linguistics)|areal feature]]s".

One should be careful about the underlying classification principle for groups of languages which have apparently a geographical name: besides areal linguistic units, the [[taxa]] of the genetic classification ([[language family|language families]]) are often given names which themselves or parts of which refer to geographical areas.

== Controlled languages ==
{{main|Controlled natural language}}

Controlled natural languages are subsets of natural languages whose grammars and dictionaries have been restricted in order to reduce or eliminate both ambiguity and complexity. The purpose behind the development and implementation of a controlled natural language typically is to aid non-native speakers of a natural language in understanding it, or to ease computer processing of a natural language. An example of a widely used controlled natural language is [[Simplified English]], which was originally developed for [[aerospace]] industry maintenance manuals.

== Constructed languages and international auxiliary languages ==

{{main|Constructed language}}
{{main|International auxiliary language}}

Constructed [[international auxiliary language]]s such as [[Esperanto]] and [[Interlingua]] that have [[native speaker]]s are by some also considered natural languages.{{Fact|date=June 2008}} However, constructed languages, while they are clearly languages, are not generally considered natural languages.<ref>Gopsill, F. P., "A historical overview of international languages". In ''International languages: A matter for Interlingua''. Sheffield, England: British Interlingua Society, 1990.</ref> The problem is that other languages have been used to communicate and evolve in a natural way, while Esperanto has been selectively designed by [[L.L. Zamenhof]] from natural languages, not grown from the natural fluctuations in vocabulary and syntax. Nor has Esperanto been naturally "standardized" by children's natural tendency to correct for illogical grammar structures in their parents' language, which can be seen in the development of [[pidgin]] languages into [[creole language]]s (as explained by Steven Pinker in  [[The Language Instinct]]). The possible exception to this are true native speakers of such languages.<ref>Proponents contend that there are 200-2000 [[native Esperanto speakers|native speakers of Esperanto]].</ref> More substantive basis for this designation is that the vocabulary, grammar, and orthography of Interlingua are natural; they have been standardized and presented by a [[International Auxiliary Language Association|linguistic research body]], but they predated it and are not themselves considered a product of human invention.<ref>[[Alexander Gode|Gode, Alexander]], ''[[Interlingua-English Dictionary|Interlingua-English: A dictionary of the international language]]''. New York: Storm Publishers, 1951. (Original edition)</ref> Most experts, however, consider Interlingua to be naturalistic rather than natural.<ref>Gopsill, F. P., "A historical overview of international languages". In ''International languages: A matter for Interlingua''. Sheffield, England: British Interlingua Society, 1990.</ref> [[Latino Sine Flexione]], a second naturalistic auxiliary language, is also naturalistic in content but is no longer widely spoken.<ref>Gopsill, F. P., "Naturalistic international languages". In ''International languages: A matter for Interlingua''. Sheffield, England: British Interlingua Society, 1990.</ref>

==Natural Language Processing==
{{main|Natural Language Processing}}

Natural language processing (NLP) is a subfield of artificial intelligence and computational linguistics. It studies the problems of automated generation and understanding of natural human languages.

Natural-language-generation systems convert information from computer databases into normal-sounding human language. Natural-language-understanding systems convert samples of human language into more formal representations that are easier for computer programs to manipulate.

== Modalities ==
Natural language manifests itself in modalities other than speech.

=== Sign languages ===
{{main|Sign language}}

<!-- Commented-out "defensive" text taken from the lead; feel free to merge if you can make it sound informative rather than defensive.
Additionally, the indigenous [[Sign language|signed languages]] of the world merit inclusion as natural languages owing to extensive linguistic analysis in the latter 20th century confirming their unique and consistent [[grammar]], [[syntax]], rules and visual logic dramatically unlike the spoken languages of the nations or geographic regions in which they arose. American, French, and British Sign Languages are the best documented examples in the literature.
-->
In linguistic terms, sign languages are as rich and complex as any oral language, despite the previously common misconception that they are not "real languages". Professional linguists have studied many sign languages and found them to have every linguistic component required to be classed as true natural languages<ref>[http://homepage.mac.com/trevor.a.johnston/.Public/PhDChp1.pdf Auslan: the Sign Language of the Australian Deaf Community. Volume One, Chapter 1]</ref>.

Sign languages are not [[pantomime]], much as most spoken language is not [[onomatopoeic]]. The signs do tend to exploit iconicity (visual connections with their referents) more than what is common in spoken language, but they are above all conventional and hence generally incomprehensible to non-speakers, just like spoken words and morphemes<ref>[http://homepage.mac.com/trevor.a.johnston/.Public/PhDChp6.pdf Auslan: the Sign Language of the Australian Deaf Community. Volume One, Chapter 6]</ref>. They are not a visual rendition of an oral language either. They have complex grammars of their own, and can be used to discuss any topic, from the simple and concrete to the lofty and abstract.

=== Written languages ===
{{main|Written language}}

In a sense, written language should be distinguished from natural language. Until recently in the developed world, it was common for many people to be fluent in [[spoken language|spoken]] or [[sign language|signed languages]] and yet remain illiterate; this is still the case in poor countries today. Furthermore, natural [[language acquisition]] during childhood is largely spontaneous, while [[literacy]] must usually be intentionally acquired.
<ref>Pinker, Steven. 1994. The Language Instinct</ref>

== See also ==

* [[Language]]
* [[Natural language processing]] (NLP)
* [[Universal grammar]]
* [[LGML]] Linguistics Markup Language

== Notes ==
<references/>

== References ==
*ter Meulen, Alice, 2001, "Logic and Natural Language," in Goble, Lou, ed., ''The Blackwell Guide to Philosophical Logic''. Blackwell.

[[Category:Linguistics]]
[[Category:Natural language processing]]
[[Category:Neuropsychological assessment]]
[[Category:Language]]

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[[es:Lengua natural]]
[[eo:Natura lingvo]]
[[eu:Lengoaia natural]]
[[fa:زبان طبیعی]]
[[fr:Langue naturelle]]
[[gl:Linguaxe humana]]
[[ko:자연어]]
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[[hu:Természetes nyelv]]
[[ja:自然言語]]
[[no:Naturlig språk]]
[[pl:Język naturalny]]
[[pt:Língua natural]]
[[ksh:Natüürlijje Shprooch]]
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[[ru:Естественный язык]]
[[sr:Природни језици]]
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