  With the increasing amount of web information, questions answering systems
becomes very important to allow users to access to direct answers for their
requests. This paper presents an Arabic Questions Answering Systems based on
entailment metrics. The type of questions which this paper focuses on is why
questions. There are many reasons lead us to develop this system: generally,
the lack of Arabic Questions Answering Systems and scarcity Arabic Questions
Answering Systems which focus on why questions. The goal of the proposed system
in this research is to extract answers from re-ranked retrieved passages which
are retrieved by search engines. This system extracts the answer only to why
questions. This system is called by EWAQ: Entailment based Why Arabic Questions
Answering. Each answer is scored with entailment metrics and ranked according
to their scores in order to determine the most possible correct answer. EWAQ is
compared with search engines: yahoo, google and ask.com, the well-established
web-based Questions Answering systems, using manual test set. In EWAQ
experiments, it is showed that the accuracy is increased by implementing the
textual entailment in re-raking the retrieved relevant passages by search
engines and deciding the correct answer. The obtained results show that using
entailment based similarity can help significantly to tackle the why Answer
Extraction module in Arabic language.
