The skills needed to use language (spoken, written, signed, or otherwise communicated) to interact with others, and problems related to the development of these skills.

Experts in child development generally agree that all babies develop skills for spoken and written language according to a specific developmental schedule, regardless of the language being learned. Although the milestones follow one another in roughly the same sequence, there is significant variability from child to child as to when the first word is spoken and the first sentence is composed.

The accompanying table illustrates the developmental milestones for communication.

Language employs symbols—words, gestures, or spoken sounds—to represent objects and ideas. Communication of language begins with spoken sounds combined with gestures, relying on two different types of skills. Children first acquire the skills to receive communications, that is, listening to and understanding what they hear...