SQL unaccent is a PostgreSQL extension that removes accents (diacritic signs) from lexemes. It is a filtering dictionary that can be used to improve user experience and implement search in a user-friendly way. The unaccent() function removes accents from a given string and can be used outside normal text search contexts. For example, SELECT unaccent('unaccent', 'Hôtel') returns 'hotel'. The unaccent extension provides a single function, unaccent(), which can be used to remove accents from words. It can even be indexed using an unaccent-based index to speed up the process.