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<title>Commonly Asked Questions</title>
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<h1>What is the difference between similarity and relatedness?</h1>
<p>Semantic similarity measures quantify how ``alike'' (or similar)
two concepts are by determining their closeness in a hierarchy.
Semantic relatedness measures quantify degree of semantic feature
overlap between two terms. Two terms may be related (needle-thread)
but not necessarily similar.
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<h1>What is a Concept Unique Identifier?</h1>
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In simple terms, a Concept Unique Identifier (CUI) is a concept in the
UMLS Metathesaurus.
For a longer explanation, read on:
The UMLS Metathesaurus contains biomedical and clinical concepts
from over 100 disparate terminology sources that have been semi-
automatically integrated into a single resource containing a wide
range of biomedical and clinical information. For example, it contains
the Systematized Nomenclature of Medicine--Clinical Terms (SNOMED CT),
which is a comprehensive clinical terminology created for the electronic
exchange of clinical health information, the Foundational Model of Anatomy
(FMA), which is an ontology of anatomical concepts created specifically for
biomedical and clinical research, and MEDLINEPLUS, which is a terminology
source containing health related concepts created specifically for consumers
of health services.
The concepts in these sources can overlap. For example, the concept
Autonomic nerve exists in both SNOMED CT and FMA. The Metathesaurus
assigns the synonymous concepts from the various sources a CUI. Thus
both the Autonomic nerve concepts in SNOMED CT and FMA are assigned
the same CUI (C0206250). This allows multiple sources in the
Metathesaurus to be treated as a single resource.
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