Mental Retardation is the most common cause of delayed language development among children. It is identified at a very early age. Many people have misperceptions on the characteristics and abilities of mentally retarded children. It is important to remember that a mentally retarded child's language will not be much different from other children's language, it will just be slower.
Most children with Mental Retardation acquire a language system and functional speech. The rate and extent at which a child learns language is in proportion to the degree of the retardation. The more extensive the retardation is, the harder it is for the child to learn language. Mentally retarded children begin producing single words about 2 years later than normal children. Their vocabularies are limited, their sentences are shorter and structurally less complex than the average child's. Unlike normal learning children, mentally retarded children tend to use their speech more for demand than for conveying ideas. These children don't just have delayed learning in language, they are delayed in almost all parts of development.