The size of expressive lexicon in 18-to-36-month-old children raised in farsi-speaking families: a comparative study

Introduction: The acquisition of the lexicon is a central and complex component of language development. The ultimate goal of this study was to survey the expressive lexicon size of 18-to-36-month-old children growing up in Farsi-speaking families. Materials and Methods: In a descriptive cross-sectional study, expressive lexicon size of 42 normal children with the age range of 18 to 36 months was evaluated by CDI (form II). Subjects were divided into three age groups, each of which covered a six-month period. The forms were completed individually by each subject’s mother. Size of expressive lexicon was compared across the three age groups. Results: Generally speaking, the difference of expressive lexicon size was significant among the three studied age groups (P < 0.01). Moreover, the categories of common nouns and grammatical function words comprised the maximum (P = 0.001) and the minimum (P = 0.02) proportions of lexicon respectively. Conclusion: Study results showed that as children grew older, their respective size of expressive lexicon increased. Also, the variation of the vocabulary size for different lexical categories was wide at this age range. Keywords: Expressive lexicon, 18-36 month of age, Normal child, CD