SLI is used to refer to problems in the acquisition and use of language, typically in the context of normal development. Whether it refers to individuals with normal overall cognitive development is controversial.
Individuals with SLI exhibit problems in combining and selecting speech sounds of language into meaningful units (phonological awareness). These problems are different to speech impairments that arise from difficulties in coordination of oral-motor musculature.
Symptoms include the use of short sentences, and problems producing and understanding syntactically complex sentences. SLI is also associated with an impoverished vocabulary, word finding problems, and difficulty learning new words, whereas the basic tasks for development of phonology and syntax are completed in childhood, vocabulary continues to grow in adulthood.