 Other examples of speech-language pathology (SLP) testing instruments like the Bracken Basic Concept Scale (BBCS) and Clinical Evaluation of Language Fundamentals (CELF) evaluate a broad range of language skills which include children's acquisition of basic concepts of colours, letters, numbers, formulation of words and sentences, among other language and cognitive skills.Tests such as Peabody Picture Vocabulary Test (PPVT) assesses instead the receptive vocabulary of children, and even adults.The past works of linguists such as Crystal were applicable to a wide range of communication disorders at every linguistic level.