Developing a List of Expressive Vocabulary for Farsi-speaking Children Aged 24-48 Months: Comparison Between Down Syndrome and Typically Developing Children

Introduction: Expressive vocabulary plays a vital role in child language development, and its assessment can be one of the essential indicators to identify language developmental delay, especially in children with Down syndrome. We developed a list of expressive vocabulary and compared the size and class of expressive vocabularies between typically developing and Down syndrome children. Materials and Methods: Expressive vocabulary of 150 children was examined in this study. A total of 120 typically developing Farsi-speaking children (in four age Groups, with a 6-month interval) and 30 children with Down syndrome (aged 24-48 months) participated in this study. The parents of the children filled out the form that included 636 words from different vocabulary classes. These classes were based on studies that investigated language development in Farsi-speaking children. Results: The expressive vocabulary size in Farsi-speaking children was significantly higher than in Down syndrome children (P≤0.001). There was no statistically significant difference between boys and girls regarding expressive vocabulary size in two Groups of children. The size of nouns in all age Groups is more than other classes, and the size of conjunctions in all age Groups is less than the other ones. A direct correlation was found between age and the size of expressive vocabulary. Conclusion: According to the study findings, the list of expressive vocabulary can detect delays in developing expressive vocabulary