Morphologically rich languages like Arabic <cite>(Beesley, K. 1996</cite> ) present significant challenges to many natural language processing applications as the one described above because a word often conveys complex meanings decomposable into several morphemes (i.e. prefix, stem, suffix) . By segmenting words into morphemes, we can improve the performance of natural language systems including machine translation (Brown et al. 1993 ) and information retrieval (Franz, M. and McCarley, S. 2002) .