olemus
ISO 18587, 24620-1:
keel, mille päritolu ei ole teada, kuid mis areneb pidevalt,
kohati ainuomaselt ja on traditsiooniliselt kasutusel
inimsuhtluses
= language with its origin unknown, but continuously developing sometimes in idiosyncratic ways as is used conventionally for human communication

ISO 1087, 5127, 9241:
keel, mis on või oli aktiivselt kasutusel mingis inimkoosluses
ja mille reeglid tulenevad peamiselt ta kasutamisest
= language which is or was in active use in a community of people, and the rules of which are mainly deduced from the usage

ISO 17100:
kirjalik, märgipõhine või suuline inimkeel
= written, signed, or spoken human language

ISO/IEC 2382:
keel, mille reeglid põhinevad käibival kasutamisel,
olemata spetsiifiliselt ette kirjutatud
= a language whose rules are based on current usage without being specifically prescribed

ISO 639-4:
inimsuhtluse keel, mis pole tehiskeel
= language for human communication that is not an artificial language

ülevaateid
https://en.wikipedia.org/wiki/Natural_language

https://www.mustgo.com/worldlanguages/language-families/

https://www.uni-due.de/SHE/SHE_Indo_European.htm

http://attempto.ifi.uzh.ch/site/pubs/papers/kuhn2013cl.pdf

levik
https://en.wikipedia.org/wiki/List_of_languages_by_number_of_native_speakers

https://www.milestoneloc.com/natural-language-vs-constructed-language-vs-artificial-languages/

https://en.wikipedia.org/wiki/List_of_languages_by_total_number_of_speakers

http://www.sfs.uni-tuebingen.de/~gjaeger/lehre/ws1011/languagesOfTheWorld/folien1.pdf

https://www.visualcapitalist.com/100-most-spoken-languages/

vt ka
- loomuliku keele töötlus