Excellent question! First generation immigrants to the U.S. have often sought to forget their native languages in favor of English, so we perceive the endangerment of language all the time. The criteria that identify such perishability are the lessening of printed matter in that endangered language, the absence of new literature in that language, failure to teach that language in any schools, and lack of places set aside for speaking that language.

If the children are not speaking their mother tongue, even a language with relatively robust numbers in census data can be considered endangered. The causes of such situations are diverse and often include nationalistic policies of linguistic unification that ignore multicultural social realities and linguistic rights, as well as discrimination in its many unpleasant forms. I am attaching a PDF edition of the Universal Declaration of Linguistic Rights, drafted in 1994-1996 by an international team of activists, writers, and scholars, led by the Catalan members of PEN International, hoping that it is useful and/or interesting to you. Versions in other languages can be found on this web site: http://www.linguistic-declaration.org/index-gb.htm (go to the pages "Book of declaration" and "Other versions").

That is a fine contribution, David, like all of yours. It should be mentioned, in case Peermohammad may not know, that the Franco dictatorship in Spain between 1939 and 1975 prohibited the cultivation of the Catalan (provincial) language as subversive. Hence the Universal Declaration of Linguistic Rights is a kind of (justified) backlash on the part of its Catalan promoters. I say justified because there exists a rich literature in the Catalan language in a Catalan culture which has always been vibrant. Enthusiasm for Catalan studies has overflowed into U.S. Hispanism.

Those are good points, Nelson. One of the tasks of the Committee of Experts that drafted the Universal Declaration of Linguistic Rights was to take the initial versions, which tended to reflect the Catalan experience, and modify them to fit the sociolinguistic realities in other parts of the world. I translated one of the later drafts into Spanish (at the time there were only versions in Catalan, French, and English) and read it to the members of the Academia de Cultura Hñähñu, a group of indigenous Otomí educators from the state of Hidalgo in central Mexico. Their main concern was to emphasize the linguistic rights of communities of migrants outside of their historical homeland, since there are many such Otomí groups in cities in Mexico and especially the United States. This contrasts with the Catalan experience, since Barcelona has historically attracted speakers of Spanish and other languages. My Otomí colleagues suggested other additions to the Declaration, such as the right to revise and correct toponyms in their native language within their historical territory, and to do the same with the names of people. They felt this was necessary because of the lack of linguistic precision in the official versions of these proper names. These suggestions were taken into account in the final version of the Declaration. This document has been influential since 1996 and has inspired national linguistic rights legislation in some countries. Eighteen years later, linguistic rights have improved greatly in Mexico, where exemplary legislation was passed in 2003, including the creation of the National Institute of Indigenous Languages. Sadly, many of the 364 native language variants spoken here are endangered. Lots of people are doing what they can to try to preserve them, and government policy has turned around 180°, from policies of ethnocidal linguistic assimilation to new policies of state support for the preservation of the nation's rich linguistic heritage.

Great question; this is exactly what I was looking for.

We may not find universal criteria. They may differ across situations. The concept of endangered language in the context of immigrants, as Orringer points out, may vary from situations like India where the languages of aboriginal communities are about to die. Of course census data will be one of the criteria, but the validity and reliability of the data and the understanding of the basic terms for the data collectors also matters a lot.

When a language is at a disadvantage by the shrinking number of speakers, presence of another dominant language of opportunity, governmental discrimination ,lack of avenues of publication and rteadership , it is time for alarm bells ringing for those who care. Languages simply vanish when nobody is bothered about them.