Summary form only given. Lexicon lookup is an essential part of almost every natural language processing system. A natural language lexicon is a set of strings where each string consists of a word and the associated linguistic data. Its computer representation is a structure that returns appropriate linguistic data on a given input word. It should be small and fast. We propose a method for lexicon compression based on a very efficient trie compression method and the inverted file paradigm. The method was applied on a 664000 string, 18 Mbyte, French phonetic and grammatical electronic dictionary for spelling-to-phonetics conversion. Entries in the lexicon are strings consisting of a word, its phonetic transcription, and some additional codes.