SIL International (formerly known as the Summer Institute of Linguistics) is a evangelical Christian non-profit organization whose main purpose is to study, develop and document languages, especially those that are lesser-known, in order to expand linguistic knowledge, promote literacy, translate the Christian Bible into local languages, and aid minority language development.
Based on its language documentation work, SIL publishes a database, Ethnologue, of its research into the world's languages, and develops and publishes software programs for language documentation, such as FieldWorks Language Explorer (FLEx) and Lexique Pro.
Its main offices in the United States are located at the International Linguistics Center in Dallas, Texas.
William Cameron Townsend, a Presbyterian minister, founded the organization in 1934, after a Christian mission in the early 1930s, with the Disciples of Christ among the Kaqchikel Maya people in Guatemala. In 1933, he turned to Mexico with the purpose of translating the Bible into indigenous languages there, as he had done for Kaqchikel. Townsend established a working relationship with the Mexican Secretariat of Public Education under the government of President Lázaro Cárdenas (in office 1934-1940) and founded SIL to educate linguist-missionaries to work in Mexico. Because the Mexican government did not allow missionary work through its educational system, Townsend founded Wycliffe Bible Translators in 1942 as a separate organization from SIL. Wycliffe Bible Translators focused on Bible translation and missionary activities whereas SIL focused on linguistic documentation and literacy education.
Having initiated the collaboration with the Mexican education authorities, Townsend started the institute as a small summer training session in Sulphur Springs, Arkansas, in 1934 to train missionaries in basic linguistic, anthropological, and translation principles. Through the following decades the SIL linguists worked at providing literacy education to indigenous people of Mexico, while simultaneously working with the Wycliffe Bible Translators on Bible translation. One of the students at the first summer institute in its second year, 1935, Kenneth Lee Pike (1912–2000), would become the foremost figure in the history of SIL.  He served as SIL's president from 1942 to 1979, then as president emeritus until his death in 2000.
In 2016, Dr. Michel Kenmogne from Cameroon became president.
In 2020, the organization said it had 1,350 language projects in 104 countries and 4,300 employees from 89 countries. 
SIL's principal contribution to linguistics has been the data that have been gathered and analyzed from over 1,000 minority and endangered languages, many of which had not been previously studied academically. SIL endeavors to share both the data and the results of analysis in order to contribute to the overall knowledge of language. This has resulted in publications on languages such as Hixkaryana and Pirahã, which have challenged the universality of some linguistic theories. SIL's work has resulted in over 20,000 technical publications, all of which are listed in the SIL Bibliography. Most of these are a reflection of linguistic fieldwork.
SIL's focus has not been on the development of new linguistic theories, but tagmemics, though no longer promoted by SIL, was developed by Kenneth Pike, who also coined the words emic and etic, more widely used today in anthropology.
Another focus of SIL is literacy work, particularly in indigenous languages. SIL assists local, regional, and national agencies that are developing formal and informal education in vernacular languages. These cooperative efforts enable new advances in the complex field of educational development in multilingual and multicultural societies.
The organization has recently established a new Language and Culture Documentation Services Unit that aims to preserve and revitalize languages threatened by extinction. The creation of this department reflects a growing interest in documenting endangered languages and incorporates a multidisciplinary approach of anthropology and linguistics.
Ethnologue: A Guide to the World's Languages, is published by SIL, since 1951. Starting with the 16th ion in 2009, Ethnologue uses the ISO 639-3 standard, which assigns 3-letter codes to languages; these were derived in part from the 3-letter codes that were used in the Ethnologue's 15th ion. SIL is the registration authority for the ISO 639-3 standard. The 15th ion, which was published in 2005, includes 7,299 codes. A 16th ion was released in the middle of 2009, a 17th in 2013, and an 18th in 2015.
SIL has developed widely used software for linguistic research. Adapt It is a tool for translating text from one language into a related language after performing limited linguistic analysis. In the field of lexicon collection, ShoeBox, the newer ToolBox (Field Linguist's Toolbox), and Lexique Pro have largely been replaced by FieldWorks Language Explorer (FLEx Windows and Linux) for linguists and WeSay (also Windows and Linux) for non-professionals. Graphite is a smart-font technology and rendering system. Keyman is keyboard software solution for typing over 2000 of the world's languages as well as the ability to make custom keyboards. 
SIL has developed several widely used font sets that it makes available as free software under the SIL Open Font License (OFL). The names of SIL fonts reflect the Biblical mission of the organization "charis" (Greek for "grace"), "doulos" (Greek for "servant") and "gentium" (Latin for "of the nations"). These fonts have become standard resources for linguists working on the documentation of the world's languages. Most of them are designed only for specific writing systems, such as Ethiopic, Devanagari, New Tai Lue, Hebrew, Arabic, Khmer, Yi, Myanmar, Coptic, and Tai Viet, or some more technical notation, such as cipher musical notation or IPA. Fonts that support Latin include:
Gentium: "a typeface family designed to enable the diverse ethnic groups around the world who use the Latin, Cyrillic and Greek scripts to produce readable, high-quality publications. It supports a wide range of Latin- and Cyrillic-based alphabets."
Doulos SIL: "a Unicode serif font similar in design to Times/Times New Roman. It contains a comprehensive inventory of glyphs needed for almost any Roman- or Cyrillic-based writing system, whether used for phonetic or orthographic needs. In addition, there is provision for other characters and symbols useful to linguists. It contains near-complete coverage of all the characters defined in Unicode 7.0 for Latin and Cyrillic."
Charis SIL: "a Unicode-based font family that supports the wide range of languages that use the Latin and Cyrillic scripts. It is specially designed to make long texts pleasant and easy to read, even in less than ideal reproduction and display environments."
Andika: "a sans serif Unicode font designed especially for literacy use and the needs of beginning readers. The focus is on clear letterforms that will not be easily confused with one another. It supports near-complete coverage for Latin and Cyrillic."
The 1947 Summer Meeting of the Linguistic Society of America passed a resolution that the work of SIL "should be strongly commended by our Society and welcomed as one of the most promising developments in applied linguistics in this country."
SIL's work has received appreciation and recognition in a number of international settings. In 1973, SIL was awarded the Ramon Magsaysay Award for International Understanding. This foundation honors outstanding individuals and organizations working in Asia who manifest greatness of spirit in service to the peoples of Asia. UNESCO Literacy Prizes have been awarded to SIL's work in a number of countries: Australia (1969), Cameroon (1986), Papua New Guinea (1979), Philippines (1991).
In 1979, SIL's agreement was officially terminated by the Mexican government after critiques from anthropologists regarding the combination of education and missionary activities in indigenous communities, though SIL continued to be active in that country. At a conference of the Inter-American Indian Institute in Mérida, Yucatán, in November 1980, delegates denounced the Summer Institute of Linguistics, charging that it was using a scientific name to conceal its Protestant agenda and an alleged capitalist view that was alien to indigenous traditions. This led to the agreement with the Ecuadoran government being terminated in 1980, although a token presence remained. In the early 1990s, the Confederation of Indigenous Nationalities of Ecuador (CONAIE) demanded the expulsion of SIL from the country. SIL was also expelled from Brazil, Mexico, and Panama, and restricted in Colombia and Peru.
The organization's focus on language description, language development and Bible translation, and the missionary activities carried out by many of its field workers have been criticized by linguists and anthropologists who argue that SIL aims to change indigenous cultures, which exacerbates the problems that cause language endangerment and language death. Linguists have argued that the missionary focus of SIL makes relations with academic linguists and their reliance on SIL software and knowledge infrastructure problematic in that respective goals, while often overlapping, also sometimes diverge considerably.
SIL does not consider efforts to change cultural patterns a form of culture destruction and points out that all their work is based on the voluntary participation of indigenous peoples. In the SIL view, ethnocide is not a valid concept and it would lead to pessimism to characterize culture change resulting from the inevitable progress of civilization as ethnocide. SIL considers itself as actively protecting endangered languages by promoting them within the speech community and providing mother-tongue literacy training. Additionally, their expanded interest in preserving threatened languages has resulted in the creation of a Language and Culture Documentation Services Unit.
Besides the headquarters in Dallas, SIL has offices and locally incorporated affiliated organizations in the following countries:
^ Keith Brown, Sarah Ogilvie, Concise Encyclopedia of Languages of the World, Elsevier, Netherlands, 2010, p. 385
^Stepp, John Richard, Hector Castaneda, and Sarah Cervone. "Mountains and biocultural diversity." Mountain Research and Development 25, no. 3 (2005): 223-227. "For the distribution of languages we used the Ethnologue database produced by the Summer Institute of Linguistics (SIL). Ethnologue is widely regarded as the most comprehensive data source of current languages spoken worldwide."
^Baines, David. "FieldWorks Language Explorer (FLEx)." eLEX2009: 27.
^Butler, L., & HEATHER, V. V. (2007). Fieldworks Language Explorer (FLEx). Language documentation & conservation, 1(1).
^Rogers, C. (2010). Review of fieldworks language explorer (flex) 3.0.
^Ulinski, M., Balakrishnan, A., Bauer, D., Coyne, B., Hirschberg, J., & Rambow, O. (2014, June). Documenting endangered languages with the wordseye linguistics tool. In Proceedings of the 2014 Workshop on the Use of Computational Methods in the Study of Endangered Languages (pp. 6-14). "One of the most widely-used toolkits in the latter
category is SIL FieldWorks (SIL FieldWorks, 2014), or specifically, FieldWorks Language Explorer (FLEx). FLEx includes tools for eliciting and recording lexical information, dictionary development, interlinearization of texts, analysis
of discourse features, and morphological analysis. An important part of FLEx is its "linguistfriendly" morphological parser (Black and Simons, 2006), which uses an underlying model of morphology familiar to linguists, is fully integrated into lexicon development and interlinear text analysis, and produces a human-readable grammar sketch as well as a machine-interpretable parser. The morphological parser is constructed "stealthily" in the background, and can help a linguist by predicting glosses for interlinear texts."
^Black, H. Andrew, and Gary F. Simons. "The SIL Field-Works Language Explorer approach to morphological parsing." Computational Linguistics for Lessstudied Languages: Texas Linguistics Society 10 (2006).
^Bird, S., & Simons, G. (2003). Seven dimensions of portability for language documentation and description. Language, 557-582.
^Byfield, B. (2006). Graphite: Smart font technology comes to FOSS. Linux. com. Online: http://wwwArchived 2001-04-26 at the Wayback Machine. linux. com/articles/52884. Accessed July, 18(2007), 652.
^Epps, Patience (2005), "Language endangerment in Amazonia: The role of missionaries", in Wolgemuth, Jan; Dirksmeyer, Tyko (eds.), Bedrohte Vielfalt: Aspects of Language Death, Berlin: Weissensee: Berliner Beiträge zur Linguistik.
Hart, Laurie K. (1973), "The Story of the Wycliffe Translators: Pacifying the Last Frontiers", NACLA's Latin America & Empire Report, VII. This article describes SIL's collaboration with US oil corporations and military governments in South America in the 1950s and 1960s.
Headland, Thomas; Pike, Kenneth; Harris, Marvin, eds. (1990), Emics and etics: The insider/outsider debate, Thousand Oaks, CA: Sage Publications.
Hvalkof, Søren; Aaby, Peter, eds. (1981), Is God an American? An Anthropological Perspective on the Missionary Work of the Summer Institute of Linguistics, Copenhagen/London: A Survival International Document, International Workgroup for Indigenous Affairs, ISBN87-980717-2-6.
Lewis, Norman (2013), The Missionaries: God Against the Indians, Open Road Media, ISBN9781480433335.
Castro Mantilla, Maria Dolores (1996), El Trabajo del ILV en Bolivia, 1954–1980, Informe Final [The Work of SIL in Bolivia, 1954–1980, Final Report], LaPaz: Undersecretary of Ethnic Affairs, National Secretary of Gender and Generational Ethnic Affairs, Ministry of Human Development. This report in Spanish contains a detailed chart of SIL activities in Latin American countries.
Orlandi, Eni Pucinelli (December 1999), "Sprache, Glaube, Macht: "Ethik und Sprachenpolitik" [Language, Faith, Power: Ethics and Language Policy], Lili - Zeitschrift für Literaturwissenschaft und Linguistik (in German), J.B. Metzler Verlag, 116 (4): 116–141, doi:10.1007/BF03379140, S2CID140368171. The author presents a discourse analysis of the practices of SIL.
Stoll, David (1982), Fishers of Men or Founders of Empire? The Wycliffe Bible Translators in Latin America. A US Evangelical Mission in the Third World, London: Zed Press, ISBN0-86232-111-5. Criticism of alleged SIL missionary activities.
Willibrand, W. A. (1953), Oklahoma Indians and the Summer Institute of Linguistics.