Skip Navigation Bar

Fact Sheet
UMLS® Semantic Network

Introduction

The Unified Medical Language System® (UMLS®) Semantic Network consists of:

  1. a set of broad subject categories, or semantic types, that provide a consistent categorization of all concepts represented in the UMLS Metathesaurus®, and
  2. a set of useful and important relationships, or semantic relations, that exist between semantic types.

The Semantic Network is one of the three UMLS components: the Metathesaurus, the Semantic Network, and the SPECIALIST Lexicon. NLM updates the UMLS twice per year in May and November.

Structure and Content

The scope of the Semantic Network is broad, allowing for the semantic categorization of a wide range of terminology in multiple domains. There are 133 semantic types and 54 semantic relationships. 

Major groupings of semantic types include:

  • organism
  • anatomical structure
  • biologic function
  • chemical
  • physical object
  • idea or concept

The links between the semantic types provide the structure for the network and represent important relationships in the biomedical domain. The primary link between the semantic types is the ”isa” link. The isa link establishes the hierarchy of types within the Semantic Network and facilitates the assignment of the most specific semantic type available for a Metathesaurus concept.

There are also five major categories of non-hierarchical relationships:

  • physically related to
  • spatially related to
  • temporally related to
  • functionally related to
  • conceptually related to

Each semantic type record includes the following: a unique identifier, a tree number indicating its position in an ‘isa’ hierarchy, a definition, and its immediate parent and children.

Each semantic relationship record includes a unique identifier, a tree number, a definition, and the set of semantic types that plausibly can be linked by this relationship.

Downloading and Browsing the Semantic Network

The Semantic Network is an open source resource and it is available for download on the UMLS Semantic Network Web site. Distribution is subject to terms and conditions.

The UMLS Terminology Services (UTS) includes a Semantic Network Browser, available through the Applications menu. You must have an active UMLS Metathesaurus License to access the UTS. For instructions on requesting a license and accessing the UTS, see How to License and Access the Unified Medical Language System® (UMLS®) Data.

NLM also distributes the Semantic Network as a component of the UMLS Knowledge Sources through the Downloads menu of the UTS. You must have an active UMLS Metathesaurus License to access the UTS. For instructions on requesting a license and accessing the UTS, see How to License and Access the Unified Medical Language System® (UMLS®) Data. 

Documentation

See the UMLS Semantic Network Web site for information about the latest version of the Semantic Network.

See the Semantic Network chapter of the UMLS Reference Manual for detailed information about semantic types and semantic relations.

Other Fact Sheets in the UMLS series: UMLS MetamorphoSys, UMLS Metathesaurus, SPECIALIST Lexicon, UMLS Terminology Services, and Unified Medical Language System (UMLS).

For general information on NLM services, contact:

National Library of Medicine
Customer Service
8600 Rockville Pike
Bethesda, MD 20894
Telephone: 1-888-FINDNLM (1-888-346-3656)
email: http://www.nlm.nih.gov/contacts/contact.html
NLM Customer Service Form at http://apps.nlm.nih.gov/mainweb/siebel/nlm/index.cfm

A complete list of NLM Factsheets is available at:
(alphabetical list): http://www.nlm.nih.gov/pubs/factsheets/factsheets.html
(subject list): http://www.nlm.nih.gov/pubs/factsheets/factsubj.html

Or write to:

FACT SHEETS
Office of Communications and Public Liaison
National Library of Medicine
8600 Rockville Pike
Bethesda, MD 20894

Phone: (301) 496-6308
Fax: (301) 496-4450
email: publicinfo@nlm.nih.gov