International Journal of Computational Linguistics Research Mohammed El Amine Abderrahim 4 4 2013 http://www.dline.info/jcl/fulltext/v4n4/1.pdf This article evaluates the performance of two techniques for query reformulation in a system for information retrieval, namely, the concept based and the pseudo relevance feedback reformulation. The experiments performed on a corpus of Arabic text have allowed us to compare the contribution of these two reformulation techniques in improving the performance of an information retrieval system for Arabic texts.