The researchers' interest in the field of language teaching and learning was based on the lexicon as it represents the basis for language proficiency. As a matter of fact, it is considered as a basic input for learning it whether it is a mother tongue or a second language. Furthermore, recent studies in language teaching and learning have confirmed the importance of the lexicon in developing language skills and achieving learning goals. The lexicon is a key factor to the development of the linguistic competencies of the learner: both at the production and the understanding levels. It is also an important component of language ownership and acquiring knowledge of it while considering pedagogical problems and the educational constraints presented by the subject of educational lexicon. Taking into consideration of all what was mentioned above, we chose the subject of this research, which seeks to authenticate to which extent the morphological awareness is contributing to the development of the Arabic mental lexicon of non-Arabic speaking learners (Faculty of Theology at Sakarya University, Turkey), based on the results of researches on the relationship between linguistic awareness and language learning. We will emphasize the assumption that sensitive processes, especially morphological awareness, have an impact on the development of the lexicon. This has also implications on the processes of understanding and production.