1. A method for aligning words in parallel segments, the method comprising: calculating a first probability distribution according to a model estimate of word alignments within a first corpus comprising word-level unaligned parallel segments; modifying the model estimate according to the first probability distribution; discriminatively re-ranking one or more sub-models associated with the modified model estimate according to word-level annotated parallel segments; and calculating a second probability distribution of the word alignments within the first corpus according to the re-ranked sub-models associated with the modified model estimate.