Disorders of speech development are among the most common developmental disorders in early childhood. Against the backdrop of the heterogeneity of the disorder's presentation and the dependence of the symptoms on the age of the affected children, the diagnosis of speech development disorders is correspondingly complex. Impairments can manifest at various levels, such as pronunciation, vocabulary, and grammar, and can affect both language comprehension and language production. Therefore, standardized testing procedures that meet testing quality criteria and are adapted to the developmental stage of children in preschool and elementary school age are required for reliable identification of speech development disorders. This volume first provides an overview of the course of speech development in childhood. The following sections focus on the fundamentals.