The Arabic writing system allows for two representations: vowelized or non-vowelized. The vowelized writing, which characterizes the writing in the Koran, classical literature and children's books, includes the long and short vowels and all the vowels, including the vowels that express syntax functions (the final vowels). In non-vowelized writing, only the consonants and long vowels appear. The goal of the present study was to examine syntax functions and the extent to which they influenced the reading comprehension of Arab students. Ninety students participated in the study: One group received a text and questions with full vowels, while the other group received a text and questions without short vowels. One week later, the participants were given a second task. A week later, the participants were given a text and tested for reading comprehension. Certain words in the text were highlighted, and the students were asked to explain these words and to define their syntactic function. The results showed that the students given the vowelized texts achieved significantly higher grades than those who worked on the non-vowelized texts. Moreover, it was found that the greater the student's knowledge of grammar and syntax, the better her/his understanding of the meaning of the words.