This paper calculates developmental index of language growth in Egyptian Arabic based on a corpus consists of
spontaneous speech samples from10 children 5 boys and 5 girls from 1.7 to 4 years. Depending on 30 minutes transcripts of spontaneous speech production the following properties of collected data were analysed: size of vocabulary and frequency of word use in relation to age (development of types and tokens) and individual differences in vocabulary size. The contribution of the current study lies in the use of vocabulary profile results as a measure of potential indicators of developmental language delay. The results provide a new measurement tool for lexical growth at different developmental stages.