This document specifies the characteristics of three categorial structures, representing nursing practice with the overall aim of supporting interoperability in the exchange of meaningful information between information systems in respect of nursing diagnoses, nursing actions and nurse sensitive outcomes. Categorial structures for nursing diagnoses, nursing actions and nurse sensitive outcomes support interoperability by providing common frameworks with which to: a) analyse the features of different terminologies, including those of other healthcare disciplines, and to establish the nature of the relationship between them[3] [8], b) develop terminologies for representing nursing diagnoses, nursing actions[9] [12],, and nurse sensitive outcomes. c) develop terminologies that are able to be related to each other[3][8][13], and d) establish relationships between terminology models, information models and ontologies in the nursing domain[14] [16]. There is early evidence that the categorial structures can be used as a framework for analysing nursing practice[17] and for developing nursing content of electronic record systems[18][19]. This document is applicable to the following user groups: developers of terminologies that include nursing diagnosis, nursing action and nurse sensitive outcome concepts; developers of categorial structures and terminologies for other healthcare domains, to support clarification of a relationship to or overlap with nursing concepts; developers of models for health information management systems such as electronic health records and decision support systems, to describe the expected content of terminological value domains for particular sub-categories and data elements in the information models; developers of information systems that require an explicit system of concepts for internal organization, data repository management or middleware services; developers of software for natural language processing, to facilitate harmonization of their output with coding systems. It is not intended for use by clinical nurses without health informatics expertise. However, Annex B provides an introduction to categorial structures to assist those without health informatics expertise to contribute to its development, review, implementation and evaluation. NOTE 1 Although the scope of testing and review of the first edition of this International Standard has been limited to nursing, the three categorial structures have features in common with the more general framework for clinical findings [ISO/TS 22789, the domain-specific categorial structure for surgical procedures (ISO 1828) [20], ISO EN 13940: 2015 as well as with the WHO ICHI][2]. The standard may therefore inform development of other general and domain-specific categorial structures in healthcare. Topics considered outside the scope of this document include: complete categorial structures that would cover all the potential details that could appear in expressions of nursing diagnoses, nursing actions and nurse sensitive outcomes, a detailed terminology of nursing diagnoses or nursing actions or nurse sensitive outcomes, a state model for nursing diagnoses or nursing actions or nurse sensitive outcomes, for example, provisional nursing diagnosis or absent nursing diagnosis, planned nursing action or nursing action not to be done - see Annex A, nursing diagnoses made and nursing actions undertaken by nurses working in other professional roles - see Annex A and knowledge relationships such as causal relationships between concepts - see Annex B.