Apache Lucene

Apache Lucene is a Java library that an application embeds to build a search index from its own documents and run queries against it. The project describes it as a code library and API that an application calls to add search, so the application builds the index and runs the queries itself. The project homepage names Lucene as the search core of Apache Solr, Elasticsearch and OpenSearch, which are separate products.

Lucene ships as a binary archive whose jar holds the core library, and Maven Central publishes the same core artifact. PyLucene, a Python binding, is documented on its own page of the project site.