1. A machine translation method for translating source text from a first language to target text in a second language, comprising: receiving the source text in the first language; accessing a library of bi-phrases, each of the bi-phrases including a text fragment from the first language and a text fragment from the second language, at least some of the bi-phrases comprising words tagged with restricted part of speech tags, at least one of the restricted part of speech tags configured for identifying a compoundable word from the second language in one of the bi-phrases as being one which also forms a part of a known closed compound word in the second language in another of the bi-phrases, when combined with another compoundable word, wherein: a first of the restricted part of speech tags identifies a) a compoundable word which appears in a known closed compound word in other than a head position, and a second of the restricted part of speech tags identifies at least one of: b) a compoundable word which appears in a known closed compound word in the head position, and c) another word, where the compoundable word a), and at least one of the words b) and c) identified by the first and second of the restricted part of speech tags are all a same part of speech; retrieving text fragments in the second language from the library corresponding to text fragments in the source text; generating at least one target hypothesis, each of the target hypotheses comprising text fragments selected from the retrieved text fragments in the second language; and evaluating the target hypothesis with a translation scoring function which scores the target hypothesis according to a plurality of feature functions, at least one of the feature functions being based at least in part on a combination of the first and the second of the restricted part of speech tags; and based on the evaluation, outputting one of the at least one target hypothesis as the optimal hypothesis for forming the translation; and wherein at least one of the accessing, retrieving, evaluating and outputting is performed with a computer processor.