Peter K Austin has published 11 books on minority and endangered languages, including 12 Australian Aboriginal languages, and holds the Märit Rausing Chair in field linguistics at the School of Oriental and African Studies where he is also director of the Endangered Languages Academic Programme. His most recent book is 1000 Languages: The Worldwide History of Living and Lost Tongues, which explores the state of languages around the world.

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There are more than 6,900 languages used around the world today, ranging in size from those with hundreds of millions of speakers to those with only one or two. Language experts now estimate that as many as half of the existing languages are endangered, and by the year 2050 they will be extinct. The major reason for this language loss is that communities are switching to larger politically and economically more powerful languages, like English, Spanish, Hindi or Swahili.

Each language expresses the history, culture, society and identity of the people who speak it, and each is a unique way of talking about the world. The loss of any language is a loss to both the community who use it in their daily lives, and to humankind in general. The songs, stories, words, expressions and grammatical structures of languages developed over countless generations are part of the intangible heritage of all humanity.

So how to choose a top 10 from more than 3,000 endangered languages? My selection is a personal one that tries to take into account four factors: (1) geographical coverage - if possible I wanted at least one language from each continent; (2) scientific interest - I wanted to include languages that linguists find interesting and important, because of their structural or historical significance; (3) cultural interest - if possible some information about interesting cultural and political aspects of endangered languages should be included; and (4) social impact - I wanted to include one or more situations showing why languages are endangered, as well as highlighting some of the ways communities are responding to the threat they currently face.

1. Jeru

Jeru (or Great Andamanese) is spoken by fewer than 20 people on the Andaman Islands in the Indian Ocean. It is generally believed that Andamanese languages might be the last surviving languages whose history goes back to pre-Neolithic times in Southeast Asia and possibly the first settlement of the region by modern humans moving out of Africa. The languages of the Andamans cannot be shown to be related to any other languages spoken on earth.

2. N|u (also called Khomani)

This is a Khoisan language spoken by fewer than 10 elderly people whose traditional lands are located in the Kalahari Gemsbok National Park in South Africa. The Khoisan languages are remarkable for having click sounds – the | symbol is pronounced like the English interjection tsk! tsk! used to express pity or shame.The closest relative of N|u is !Xóõ (also called Ta'a and spoken by about 4,000 people) which has the most sounds of any language on earth: 74 consonants, 31 vowels, and four tones (voice pitches).

3. Ainu

The Ainu language is spoken by a small number of old people on the island of Hokkaido in the far north of Japan. They are the original inhabitants of Japan, but were not recognised as a minority group by the Japanese government until this year. The language has very complicated verbs that incorporate a whole sentence's worth of meanings, and it is the vehicle of an extensive oral literature of folk stories and songs. Moves are underway to revive Ainu language and cultural practices.

4. Thao

Sun Moon Lake of central Taiwan is the home of the Thao language, now spoken by a handful of old people while the remainder of the community speaks Taiwanese Chinese (Minnan). Thao is an Austronesian language related to languages spoken in the Philippines, Indonesia and the Pacific, and represents one of the original communities of the Austronesians before they sailed south and east over 3,000 years ago.

5. Yuchi

Yuchi is spoken in Oklahoma, USA, by just five people all aged over 75. Yuchi is an isolate language (that is, it cannot be shown to be related to any other language spoken on earth). Their own name for themselves is Tsoyaha, meaning "Children of the Sun". Yuchi nouns have 10 genders, indicated by word endings: six for Yuchi people (depending on kinship relations to the person speaking), one for non-Yuchis and animals, and three for inanimate objects (horizontal, vertical, and round). Efforts are now under way to document the language with sound and video recordings, and to revitalise it by teaching it to children.

6. Oro Win

The Oro Win live in western Rondonia State, Brazil, and were first contacted by outsiders in 1963 on the headwaters of the Pacaas Novos River. The group was almost exterminated after two attacks by outsiders and today numbers just 50 people, only five of whom still speak the language. Oro Win is one of only five languages known to make regular use of a sound that linguists call "a voiceless dental bilabially trilled affricate". In rather plainer language, this means it's produced with the tip of the tongue placed between the lips which are then vibrated (in a similar way to the brrr sound we make in English to signal that the weather is cold).

7. Kusunda

The Kusunda are a former group of hunter-gatherers from western Nepal who have intermarried with their settled neighbours. Until recently it was thought that the language was extinct but in 2004 scholars at Tribhuvan University in Kathmandu located eight people who still speak the language. Another isolate, with no connections to other languages.

8. Ter Sami

This is the easternmost of the Saami group of languages (formerly called Lapp, a derogatory term), located on the Kola Peninsula in Russia. It is spoken by just 10 elderly people among approximately 100 ethnic Ter Sami who all now speak Russian as their daily language. Ter Sami is related to Finnish and other Uralic languages spoken in Russia and Siberia, and distantly to Hungarian.

9. Guugu Yimidhirr

Guugu Yimidhirr is an Australian Aboriginal language spoken at Hopevale near Cooktown in northern Queensland by around 200 people. A wordlist was collected by Captain James Cook in 1770 and it has given English (and the rest of the world's languages) the word kangaroo. Guugu Yimidhirr (like some other Aboriginal languages) is remarkable for having a special way of speaking to certain family members (like a man's father-in-law or brother-in-law) in which everyday words are replaced by completely different special vocabulary. For example, instead of saying bama dhaday for "the man is going" you must say yambaal bali when speaking to these relatives as a mark of respect and politeness.

10. Ket

Ket is the last surviving member of a family of languages spoken along the Yenesei River in eastern Siberia. Today there are around 600 speakers but no children are learning it since parents prefer to speak to them in Russian. Ket is the only Siberian language with a tone system where the pitch of the voice can give what sound like identical words quite different meanings. (Much like Chinese or Yoruba). To add to the difficulty for any westerner wishing to learn it, it also has extremely complicated word structure and grammar.