Definition of delayed language development in children: A child with delayed language development is a child who, for various reasons, is not able to understand and express language with speech symbols and communicate with others in daily life in the same way as a normal child for the expected period of time. Common causes of language delay: There are many causes of language delay in children, including visual impairment, auditory impairment (deafness, hard of hearing, etc.), interaction disorders (autism, autistic tendencies, etc.), mental retardation, uncomfortable language environment, morphological and motor abnormalities of the articulatory organs, brain underdevelopment, and brain injury. The common assessment method for language delay in China is: S-S language delay examination method. (Sign-Significate reations) The S-S method is applicable to children with speech delay due to various reasons. Treatment for language delay: 1. play therapy 2. gesture-symbol training 3. word training 4. training in the relationship between symbolic form and instructional content 5. communication training