1. A method for grapheme-phoneme conversion of a word which is not contained as a whole in a pronunciation lexicon, comprising: decomposing the word into subwords; performing grapheme-phoneme conversion of the subwords to obtain transcriptions of the subwords; sequencing the transcriptions of the subwords are sequenced to produce at least one interface between the transcriptions of the subwords, determining phonemes of the subwords bordering on the at least one interface; determining graphemes of the subwords which generate the phonemes bordering on the at least one interface; and recalculating grapheme-phoneme conversion of the graphemes bordering on the at least one interface.