This commentary is on the original article by Caynes et al. on pages 805-812 of this issue.Two new validated measures of communication function in children have recently been reported, with somewhat confusingly similar titles: the Communication Function Classification System (CFCS) 1,2 and the Functional Communication Classification System (FCCS). 3 The interest in classifying communication function follows the International Classification of Functioning, Disability and Health approach, and meets the clinical need to support families, the children's workforce, and indeed children themselves to identify child communication abilities in 'real-life' contexts.Both the CFCS and the FCCS began as classifications for children with cerebral palsy. The CFCS later established validity for young children with a range of speech and language disorders. 1 The FCCS retains a focus on cerebral palsy, including some children using augmentative and alternative communication (AAC), with Caynes et al. 3 extending the age range to 5 to 18 years. Across this age range, FCCS scores correlated with the presence or absence of concomitant impairments of speech, gross and fine motor skills, and sensory and intellectual development. FCCS scores from a speech and language therapist unfamiliar with the child, from their parent, and from the parent responding on how the child communicated with an unfamiliar communication partner showed concurrent validity with the standardized Clinical Evaluation of Language Fundamentals (CELF-4) Pragmatics Profile. (The authors suggest the published elicitation procedures in the newer CELF-5 Pragmatics Profile could now be used by clinicians unfamiliar with the child, to further standardize clinical procedures). FCCS procedures proved feasible across the 5-to 18-year age range, although the authors suggest that some FCCS prompt questions describing communication scenarios might usefully be adapted to provide functional communication examples for older children. The study thus developed robust psychometric techniques to further establish a procedure to classify functional communication, adding to the small number of validated communication measures for children with neurodevelopmental disabilities.A commentary 4 on an earlier FCCS article 5 underlined its sound grounding in theoretical accounts of the constituents of communicative competence and in clinical requirements for reliable measures. The FCCS produces five classification levels, from children who communicate effectively, perhaps using AAC, in most situations (Level I) through those who need help in communicating with unfamiliar people or in unfamiliar environments, to those whose communication is 'unintentional', relying on others to anticipate, observe, and interpret their behaviours (Level V). By considering the child's communication, the communication situation, and the responses required of communication partners, and by offering operational definitions interpretable to families and other non-specialists, a clinically useful classification has bee...