Non-specialists can identify three types of developmental language disorder. (1) mixed receptive/expressive disorders, which impair phonology, syntax, and semantics. Children who understand nothing are nonverbal, in others speech is sparse, nonfluent, poorly intelligible, and agrammatic; (2) expressive disorders with adequate comprehension affect phonologic production-predominantly. Children with verbal dyspraxia, the most severe variant, may also be nonverbal but comprehend well; (3) higher order processing disorders affect semantics, pragmatics, and discourse. Semantics and pragmatics are invariably affected in preschool autistic children in whom isolated expressive deficits do not occur. Etiology of developmental language disorders is predominantly genetic. Structural brain lesions detectable by neuroimaging are exceptional. Severe receptive deficits require a sleep EEG to detect subclinical epilepsy. Early educational intervention is both critical and efficacious.