Q. when is a child's communication considered delayed

A child's language development is dependent on many factors, including whether there is a cleft palette, deafness, or other physical impairments, as well as developmental delays or other factors that could affect speech.

Sample articles:

Unhjem, A., Eklund, K., & Nergård-Nilssen, T. (June 01, 2015). Early Markers of Language Delay in Children with and without Family Risk for Dyslexia. First Language, 35, 3, 254-271. http://saintleo.worldcat.org/oclc/6001103794

So, W.-C., Wong, M. K.-Y., Lui, M., & Yip, V. (November 01, 2015). The Development of Co-Speech Gesture and Its Semantic Integration with Speech in 6- to 12-Year-Old Children with Autism Spectrum Disorders. Autism: the International Journal of Research and Practice, 19, 8, 956-968. http://saintleo.worldcat.org/oclc/6001099280