A method of translating an input sentence in a source language to an output sentence in a target language uses a store comprising a plurality of example sentences. A base example sentence is chosen from the store based on a comparison of the input sentence with a plurality of example sentences, and its paired translation is used as a translation basis. A portion of the input sentence differing from a corresponding portion of the base example sentence is identified. A portion of the translation basis aligned with the base example unmatched is located. The input unmatched portion is used to select a set of subsidiary example sentences from the store. A choice of possible translations corresponding to the input unmatched portion is determined from the set of subsidiary example sentences. A translation is selected from the choice based on a predetermined selection algorithm.