The construction of minimal acyclic deterministic partial finite automata to represent large natural language vocabularies is described. Applications of such automata include: spelling checkers and advisers, multilanguage dictionaries, thesauri, minimal perfect hashing and text compression. Part of this research was supported by a grant awarded by the Brazilian National Council for Scientific and Technological Development (CNPq) to the second author. Authors' Address: Cl'audio L. Lucchesi and Tomasz Kowaltowski, Department of Computer Science, University of Campinas, Caixa Postal 6065, 13081 Campinas, SP, Brazil. E-mail: lucchesi@dcc.unicamp.br and tomasz@dcc.unicamp.br. 1 Introduction The use of finite automata (see for instance [5]) to represent sets of words is a well established technique. Perhaps the most traditional application is found in compiler construction where such automata can be used to model and implement efficient lexical analyzers (see [1]). Applications of finit...