The purpose of this meta-synthesis is to formulate a hypothesis concerning the importance of diacritical marks in Arabic word recognition for typically developed Arabic readers. I propose that the importance of diacritical marks in Arabic word recognition varies as a function of grade level, stimuli frequency, and text affiliation. Stimuli commonly affiliated with narrative and informational texts are more easily read with diacritical marks in lower primary grades, where phonological recoding is the dominant reading strategy for accessing phonologically and semantically unfamiliar words. Four years of systematic exposure to standard Arabic can increase knowledge of morphology, vocabulary, and orthography to the point of developing a visual reading strategy that dominates word recognition. Thus, in the upper school grades, diacritical marks lose their supportive function for accessing stimuli commonly affiliated with narrative and informational texts; they eventually become a visual burden that compromises the direct visual access of words/texts, causing delayed semantic access and errors in accuracy. However, diacritical marks regain their supportive function when Arabic readers in the upper grades encounter stimuli that are more commonly affiliated with Quranic, literary, and poetic classical texts. These stimuli are known to have a low frequency of the derivatives, roots, and morphemic patterns with which readers are unfamiliar. Encountering these stimuli forces Arabic students to re-adopt a phonological recoding reading strategy. This meta-synthesis includes nine studies published between 1995 and 2020. The results reported in this meta-synthesis substantiate my hypothesis. The results reported in seven studies align with my hypothesis. The results reported in two studies that reported contradictory findings do not discredit my hypothesis, but rather contribute two additional variables that further refine my hypothesis. Overall, sufficient evidence supports the conclusion that the importance of diacritical marks in Arabic word recognition for typically developed Arabic readers varies as a function of grade level, stimuli frequency, and text affiliation. Developing a comprehensive theory concerning the importance of diacritical marks in Arabic word recognition would provide research-based evidence for purely anecdotal policies regarding the transition from vowelized to unvowelized script that have been used in Arabic educational systems for more than 70 years. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://www.proquest.com.bibliotheek.ehb.be/en-US/products/dissertations/individuals.shtml.]