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 word from the second language as being one which also forms a part of a known closed compound word; 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 based at least in part on combinations of 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.