Some speech delays are receptive language disorders, in which a child has difficulty understanding words or concepts. Children with this type of speech delay may have trouble identifying colours, body parts, or shapes. Others are expressive language disorders, in which a child has a reduced vocabulary of words and complex sentences for his or her age. A child with this type of speech delay may be slow to babble, talk, and create sentences. Often, a child with a speech delay has a combination of receptive and expressive delays.
Children with an oral motor problem—such as weakness in the muscles of the mouth or difficulty moving the tongue or jaw—that interferes with speech production have what is known as a speech production disorder.
Children may have speech delays due to physiological causes, such as brain damage, genetic syndromes, or hearing loss. Other speech delays are caused by environmental factors, such as a lack of stimulation. In many instances, however, the cause of a child’s speech delay is unknown.