olemus
Wiktionary:
1. one who negotiates between parties seeking mutual agreement

ülevaateid
https://www.weinbergermediation.com/faq/what-is-the-difference-between-mediators-and-lawyers/

https://corporate.findlaw.com/litigation-disputes/what-is-mediation-and-how-does-it-work.html

https://en.wikipedia.org/wiki/Mediation