SNOMED CT Components


SNOMED CT concepts represent clinical ideas, ranging from abscess to zygote.

  • Every concept has a unique numeric code known as the "concept identifier".
  • Concepts are organized in hierarchies, from the general to the specific. This allows detailed clinical data to be recorded and later accessed or aggregated at a more general level.
  • There are well over 300,000 active concepts in the SNOMED CT.


SNOMED CT descriptions link appropriate human-readable terms to concepts. A concept can have several associated descriptions, each representing a synonym that describes the same clinical idea. 

  • There are nearly a million English descriptions in the International Release of SNOMED CT.
  • Each translation of SNOMED CT includes an additional set of descriptions, which link terms in another language to the same SNOMED CT concepts.


SNOMED CT relationships link each concept to other concepts that have a related meaning. These relationships provide formal definitions and other characteristics of the concept.

  • One type of link is the "is a" relationship which relates a concept to the its more general concepts. For example, the concept "viral pneumonia" has an "is a" relationship to the more general concept "pneumonia". These "is a" relationships define the hierarchy of SNOMED CT concepts.
  • Other types of relationship represent other aspects of the definition of a concept. For example, the concept "viral pneumonia" has a "causative agent" relationship to the concept "virus" and a "finding site" relationship to the concept "lung".
  • There are well over a million relationships in SNOMED CT.



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