1. A translation memory comprising: an aligned file having a number of source language text segments encoded in a computer readable format, each of the source language text segments positioned at a unique address and paired with a target language text segment encoded in the computer readable format; an inverted index comprising a listing of source language letter n-grams, wherein each listed letter n-gram includes an associated entry for an entropy weight for the listed letter n-gram, a count of the number of source language text segments in the aligned file that include an entry for the listed letter n-gram, and a pointer to a unique location in the translation memory; and a posting vector file having a posting vector associated with each listed letter n-gram in the inverted index, each posting vector positioned at one of the unique locations pointed to in the inverted index, each posting vector including: i) a plurality of document identification numbers each corresponding to a selected one of the source language text strings in the aligned file, and ii) a number of entropy weight values, each of the number of entropy weight values associated with one document identification number.