Abstract Arabic language has a complex morphological structure, which makes it hard to select index terms for an IR system. The complexity of the Arabic morphology caused by multimode terms, using diacritics, letters have different forms according to its location in the word and affixes can be added at all locations in a word. Several methods were proposed to overcome these problems; such as root extraction and light stemming. Light stemming show better retrieval efficiency, Light10 is the best stemmer among a series of light stemmers, it simply removes suffixes and prefixes if it is listed in a predefined table. Light10 has no restrictions on the affixes, so it is possible to have two different terms having the same token while they have different meanings. This paper proposes CondLight stemmer which adds new prefixes and suffixes to the table of Light10, and imposes a set of conditions on removing these affixes. The implementation and testing of the proposed method show that CondLight gains 38% precision, while Light10 stemmer gains average precision of 36.7%. Moreover CondLight show better average precision either when imposing all conditions or part of them.

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[25] Taghva K., Elkhoury R., and Coombs J., Arabic Stemming Without A Root Dictionary, in Proceedings of International Conference on Information Technology: Coding and Computing, Las Vegas, pp. 152-157, 2005. Yaser Al-Lahham has received the B.S degree from University of Jordan in 1985, the M.S. degree from Arab Academy (Jordan) in 2004, and the PhD in Computer science from Bradford University (UK) in 2009. He is working as an assistant professor in the Department of Computer Science at Zarqa University in Jordan. His research interest includes P2P information retrieval systems, text clustering, and Databases. Mohammad Hassan has received his BS degree from Yarmouk University in Jordan in 1987, the MS degree from University of Jordan, in 1996, and the PhD degree in computer information systems from Bradford University, UK in 2003. He is working as an associate professor in the department of computer science at Zarqa University in Jordan. His research interest includes information retrieval systems and database systems. Khawla Al Matarneh has received her BS degree in computer science from Mua ta University in Jordan in 2004, the MS degree in computer science from Zarqa University, in 2017. Her research interest includes information retrieval systems and database systems.