Jan Niecislaw Baudouin de Courtenay (March 13rd 1845 - November 3rd 1929) was a Polish, known linguist for his theory of the Phonème and the phonetic alternation. He worked throughout his life in various universities of the imperial Russia: University of Kazan (1874 - 1883), University of Tartu in Estonia (1883 - 1893), University jagellonne of Cracow (1893 - 1899) and the University of Saint-Pétersbourg (1900 - 1918)), where it was known under the name of ИванАлександровичБодуэндеКуртенэ (Ivan Aleksandrovitch Bodouine de Kourtine). Between 1919 and 1929, he was professor in the Université of Warsaw, after the independence of the Poland.

Jan was born on March 13rd 1845 with Radzymin, close to Warsaw, in a family of remote French origins. One of its ancestors was a French aristocrat who emigrated during the reign Auguste II of Poland. In 1862, Baudouin entered the Université of Warsaw, called at the time principal Université . In 1866, it obtained a diploma of history and philosophy and gained a grant of the Minister of education of the imperial Russia. Leaving the Poland, he studied in various foreign universities, of which the Université Charles of Prague, the Université of Iéna and the Université Humboldt of Berlin. In 1870, it obtained the Doctorat Université of Leipzig for its report on the Polish language : On the old Polish language former to XIVe century .

Baudouin establishes the school of linguistics of Kazan in the middle of the years 1870 and was professor in the university starting from 1875. Later, it was named with the head of the faculty of linguistics of the Université of Tartu, in Estonia, at the time, Université of Yuryev, where it was in station of 1883 with 1893. Between 1894 and 1898, it was at the same station with the Université jagellonne of named Cracow then with Saint-Pétersbourg, where it continued to refine his theory of the phonetic alternations. After the independence of the Poland in 1918, it turned over to Warsaw, where it was the heart of the faculty of linguistics of the Université of Warsaw. Since 1887, it had a permanent headquarter in the Polish academy of competences and since 1897, he was member of the Academy of Science of Saint-Pétersbourg. In 1925, it was one of the founders of the Société Polonaise of Linguistics.

Work of Baudouin had an impact decisive on the linguistics of the XXe century, and been used as base at various schools of Phonologie. It was a precursor of the synchronic linguistic , the study of the contemporary spoken languages. It had an important influence on the Structuralisme, theory linguistic of the Swiss Linguiste Ferdinand de Saussure. Among most notable of its completions is the distinction between dynamic statics and languages and Langue, group of abstracted elements, and the Parole, its individual application. With its student Mikołaj Kruszewski, he also invented the term Phonème.

Three major schools of Phonologie of the XXe century directly were born from its physiophonetic distinction between alternations phonological and morphophonologic psychophonetic : the School of Phonology of Leningrad, the School of Phonology of Moscow and the School of Phonology of Prague. The three developed various positions on the nature of the dichotomy of Baudouin. The School of Prague was more known for its linguistic work on the Slavic languages. Throughout his career, Baudouin wrote scientific hundreds of articles in Polish, Russian, Czech, Slovenien, Italian, French and German.

Apart from his academic work, Baudouin de Courtenay was in favor of the revival of the various national minorities and the ethnicities. In 1915, it was stopped by the Okhrana, Russian secret police, to have published a booklet on the autonomy of the people under Russian governorship. It spent three months in prison. In 1922, without it of knowing though it is, the national minorities of Poland proposed it like candidate for the presidential ones, but was beaten with the third turn with the Polish Parlement and Gabriel Narutowicz was selected. It was also a active esperantist and chair Association Polonaise of Esperanto.

In 1929, it died in Warsaw. His/her daughter, Cezaria Baudouin de Courtenay Ehrenkreutz Jędrzejewiczowa was one of the founders of the School Polonaise of ethnology and anthropology and professor in the universities of Vilnius and Warsaw.