Definition: information element within the structure of a concept system that is a pointer or placeholder linking one or several synonymous terms with a given concept definition representation and also used in the representation of relations between concepts.

• In many modern concept systems designed for use with Information Technology, the concept system node has as a key component a numeric concept identifier. Where a concept system exists in graph-theoretical form, this can be thought of as a node or vertex of the graph. The edges of the graph then represent relations between the concepts represented by the corresponding nodes.
• When SNOMED CT, for example, uses the term "concept", then what it means is "concept system node" in the terminology advanced here. Certainly SNOMED officially defines "concept" as meaning: “unit of thought”. When we inspect its actual practice, however, then we discover that concepts in SNOMED CT are used as pointers which allow the capturing of relationships of synonymy between terms (there called "descriptions") and also of associations with other concept nodes as well as with related attributes. This is also the most common meaning of "concept" in information model standards for Electronic Health Records or other health informatics standards such as the HL7 RIM or CEN message standards.