A language delay is a delay in acquisition of language skills compared to one’s chronological and cognitive/intellectual age peers. A young child with a language delay may exhibit a slower onset of usage of a language skill, rate of progression through the acquisition process, sequence in which the language skills are learned, or all of the above. Generally, early language delay (late talking) may be characterized by less than 50 words at 24 months, few word combinations at 30 months, limited use of gestures and sounds to communicate, limited symbolic play, limited understanding of word meaning and inability to follow verbal instructions. Approximately 50 to 70 percent of these youngsters (i.e., late talkers) reportedly catch up to peers and demonstrate normal language development by preschool and school age. However, there is a subset of children who continue to demonstrate persistent difficulties acquiring and using language skills below chronological age expectations (by preschool or school age) that cannot be explained by other factors (e.g., low nonverbal intelligence, sensory impairments or autism spectrum disorder) and may be identified as having a specific language impairment (i.e., language disorder).

The American Speech-Language Hearing Association (ASHA) defines a language disorder as a significant impairment in the acquisition and use of language across modalities (e.g., speech, sign language, or both) due to deficits in comprehension and/or production across any of the five language domains (i.e., phonology, morphology, syntax, semantics, pragmatics). Language disorders are heterogeneous, and the nature and severity of disorders can vary considerably.