The CAS Lexicon is the standardized terminology that is used when indexing references. These terms are also referred to as Concepts. The CAS Lexicon is the underlying mechanism for the Precision Search that allows for synonym matching for concepts. You can search directly in the CAS Lexicon to find concepts relevant to your topic of interest, and view the hierarchy of terms to construct a complex search query:
Here you can search the Lexicon, and once you select a term, you can see it in the hierarchy. You'll have the ability to see the synonyms associated with the term, as well as broader concepts, narrower concept, and related concepts. Use the 'Add to Query' button and as you add terms, you'll select the appropriate Boolean logic to craft your query and then search:
Tip: Check out the scope notes that a Lexicon term might have to give some context as to how it is defined. These notes can be seen as a question mark next to the entry, hover over is to see a definition of the term:
Not all terms have scope notes available.
Last updated 8/8/2025
You can not use the browser's page navigation (i.e. back/forward) when using the CAS Lexicon builder. If you want to edit the query that you have built, you can do so from the right box of the query builder by deleting terms:
Do you have a suggestion for a Concept term that is not currently in the Lexicon? Or do you have suggestions for additional synonyms or synonyms that don't make much sense? Reach out to the CAS Customer Center with your thoughts and they'll engage the appropriate experts to review your thoughts and make a decision.
