Language is an important part of our culture and allows the exchange of thoughts and feelings as well as the acquisition of knowledge. Deficits in language abilities can appear at different linguistic levels (phonetics/phonology, lexicon/semantics, syntax/morphology, and pragmatics). This can concern both language comprehension and speech production in different ways. The different linguistic levels should be considered in the diagnosis of developmental language disorders. In particular, the German guidelines "Interdisziplinare S2k-Leitlinie" support this approach. This paper gives an overview of the symptoms of specific language disorder as well as its classification in the DSM-5 and the ICD-10. Moreover, there is an outlook toward the ICD-11, with explanations based on the Beta-Draft. The similarities and differences of the three diagnostic systems are pointed out and discussed. Furthermore, reference is made to the Interdisziplinare S2k-Leitlinie. While there is a distinction between expressive and receptive language disorders in the ICD-10, in the DSM-5 the two disorders are summarized in one clinical picture. In the current ICD-11 Beta-Draft, the disorders are still divided; however, they are subordinate to a common category. This represents a compromise between the two approaches. Additionally, the DSM-5 is supplemented by the diagnosis of social (pragmatic) communication disorder, and it is likely that the disorder will be included in the ICD-11 (developmental language disorder with impairment of mainly pragmatic language), too. The disorder is characterized by deficits in verbal and nonverbal communication. Future research should consider pragmatic aspects of language. The overview shows that there are no uniform diagnostic criteria. Furthermore, none of the illustrated systems considered the individual linguistic level of language, as is suggested in the Interdisziplinare S2k-Leitlinie. Although the ICF-CY also cannot capture all the linguistic levels, it enables a comprehensive description of impairments and abilities. In the differential diagnosis, a mental retardation must be excluded by nonverbal intelligence diagnosis. This is controversial because it is difficult to implement in logopedics practice and speech therapy. Moreover, in the diagnosis of specific language disorders the double discrepancy criterion must be scrutinized. In the current Interdisziplinare S2k-Leitlinie, this criterion was waived because of the controversy. In practice, the different definitions and classifications of specific language disorders lead to significant variations in the data on prevalence. Additionally, the causal research and effectiveness tests of therapeutic interventions are complicated. Moreover, for a long period there was no uniform standard in the design of assessments for diagnosis. The reliable diagnosis of language developmental disorders requires a comprehensive interdisciplinary classification.