What is the name of Google's semantic knowledge database used to enhance search results?

Google's semantic knowledge database used to enhance search results is called the Knowledge Graph. It organizes information about real-world entities and the relationships between them.

Google announced the Knowledge Graph on May 16, 2012. Its purpose was to help Search understand things rather than merely match strings of text. When someone searches for a person, place, organization, or concept, the Knowledge Graph can help Google connect related facts and display a knowledge panel alongside ordinary results.

The system draws information from multiple sources, including Wikipedia, Wikidata, structured data on web pages, and other public databases. It was also powered in part by Freebase, an open knowledge repository that Google acquired and later discontinued. The Knowledge Graph is not itself the same as Wikipedia, Wikidata, DBpedia, or Freebase; those are separate sources or projects that may contribute data to Google's broader system.

The term knowledge graph is also used generically for graph-structured knowledge bases. In this question, however, the capitalized name identifies Google's particular search-enhancement system.