1. A word alignment system, comprising: a weighted linear word alignment model, linearly combining feature values for a plurality of different features, given a word alignment for a pair of text fragments, each of the different features being weighted by a corresponding feature weight, wherein the plurality of different features in the word alignment model comprise a word association metric indicative of a strength of association between words in the pair of text fragments, the word association metric either being based on surface statistics from a training corpus, or being a conditional link probability word association metric; an automatic training component configured to train the feature weights; and a word alignment component configured to receive the pair of text fragments and access the word alignment model to identify a best scoring word alignment for the pair of text fragments.