The mental lexicon constitutes a dynamic cognitive system through which lexical items are acquired, organized, stored, interconnected, and retrieved during language comprehension and production. This study examines the principal mechanisms and methods involved in the formation and acquisition of the Arabic mental lexicon from both theoretical and applied perspectives. It focuses on the phonological, morphological, syntactic, and semantic components that shape lexical knowledge and enable speakers to process and use Arabic vocabulary effectively. The study also considers the contribution of the Holy Quran, Arabic poetry, literary and linguistic texts, everyday language use, cultural interaction, formal education, and modern scientific disciplines to the expansion of learners’ lexical repertoires. Drawing on a descriptive and analytical approach, the article explains how auditory perception, morphological derivation, syntactic organization, semantic association, repetition, contextual exposure, and active language practice facilitate the storage and retrieval of lexical units. Particular attention is given to the distinctive derivational and structural properties of Arabic and their role in establishing connections among roots, patterns, meanings, and grammatical functions within the mind. The study argues that lexical acquisition is a continuous process extending from early childhood through the successive stages of education and intellectual development. It concludes that combining the Arabic linguistic heritage with insights from psycholinguistics, cognitive linguistics, neurolinguistics, computational linguistics, and language education can strengthen lexical competence. Such integration may contribute to developing learners who are linguistically proficient, cognitively flexible, and capable of employing Arabic creatively in traditional and contemporary contexts.