[meeper16]

It's also used in AI-based document summarization systems that are worth millions e.g.

Yahoo Paid $30 Million in Cash for 18 Months of Young Summly http://allthingsd.com/20130325/yahoo-paid-30-million-in-cash...

Google Buys Wavii For North Of $30 Million http://techcrunch.com/2013/04/23/google-buys-wavii-for-north...

[yannyu]

Also used extensively in Lucene based search engines such as Solr and Elastic. Most companies running search use a Lucene-based search engine.

https://lucene.apache.org/

http://lucene.apache.org/solr/

https://www.elastic.co/