# ping-pong lemma

> theorem about sufficient conditions for ensuring that that several elements in a group acting on a set freely generate a free subgroup of that group

**Wikidata**: [Q7195651](https://www.wikidata.org/wiki/Q7195651)  
**Wikipedia**: [English](https://en.wikipedia.org/wiki/Ping-pong_lemma)  
**Source**: https://4ort.xyz/entity/ping-pong-lemma