20. The method of claim 19, wherein the list of target words contains a null word, when the probability of the fertility of the source word being equal to zero is greater than the probability of the fertility of the source word being equal to a value other than zero.
19. A method for translating a series of source words in a first language to a series of target words in a second language, comprising the steps of: inputting the series of source words; generating at least one fertility hypotheses for a fertility of a source word, based on a source word and a context of the source word; generating sense hypotheses for a translation of the source word, based on the source word and the context of the source word; determining a probability of a fertility of a source word, based on the source word and the context of the source word; determining a probability of a target word being a correct translation of the source word, based on the source word and the context of the source word; and generating a list of target words for the translation of the source word, based on the probability of the fertility and the probability of the target word.