Lecturer at the Institute of Polish Language of the University of Warsaw, full professor, editor-in-chief of the “Prace Filologiczne” periodical. Scholarly interests: dialectology, lexicography of the vernacular, language-based contacts, Polish language outside Poland, Polish language history, onomastics. Author of 253 works, i.a. the books Polska leksykografia gwarowa (Lexicography of the Vernacular), Język polski pogranicza litewsko-łotewsko-białoruskiego w świetle frekwencji cech językowych (Polish Language of the Lithuanian-Latvian-Belarusian Borderland in the Context of Linguistic Characteristics’ Frequency), website editor, e.g. Dialekty i gwary polskie. Kompendium internetowe (Dialects and Vernacular in the Polish Language. An Online Compendium).