<n0:ComplexDefinition xmlns:n0="http://ncicb.nci.nih.gov/xml/owl/EVS/ComplexProperties.xsd#"><n0:def-definition>Concept Unique Identifiers, or CUIs, are concept numbers assigned by the National Library of Medicine (NLM). If a concept in any NCI-maintained knowledgebase exists in the NLM Unified Medical Language System (UMLS), NCI includes the NLM CUI among the information we provide about the concept.</n0:def-definition><n0:def-source>NCI</n0:def-source></n0:ComplexDefinition>