The review undertaken by Werkhoven et al. 1 on the diagnostic labels for developmental disorders is remarkable, because it discusses the meanings of these labels (including autism spectrum disorders [ASD] and attention-deficit/ hyperactivity disorder [ADHD]) in the contexts of science, therapeutics and pedagogy, society, and administration. The authors described the categorical definitions of developmental disorders in the context of several limitations such as poor sharing of scientific backgrounds, unclear indications for specific treatment options and educational programs, and their relationships to stigmatization in social contexts.Because of the excessive influence of the current operational diagnostic system, the categorical definitions of clinical disease entities have a serious limitation in that they are rooted in psychiatric symptomatology without neurobiological underpinnings. In addition, in terms of the critical conceptual distinctions of the kinds-of-kinds (in the order of natural kind, discrete kind, fuzzy kind, practical kind, and dimension), the clustered properties, non-arbitrary cutoff points, discontinuity, category boundary, and category essence are all increased.Thus, the categorical definitions for developmental disorders (i.e. ASD, ADHD) can correspond to the fuzzy kind or discrete kind, but not the natural kind. Although the categorical definitions may be expected to share the essential neurobiological underpinnings for observable symptoms and signs from the viewpoint of the 'disease essentialism paradigm,' the manifestations of ASD and ADHD are phenotypically and clinically characterized by high levels of complexity and heterogeneity. 2 Ludwig Wittgenstein proposed the philosophical concepts of family resemblance and essence. 3 He argues that things which could be thought to be connected by one essential common feature may in fact be connected by a series of overlapping similarities, where no one feature is common to all of the things. Games, which Wittgenstein used as an example to explain the notion, have become the paradigmatic example of a group that is related by family resemblances.