Sigma-Upsilon Go-Between is a term used to describe a person who acts as a liaison between two or more parties. This person is usually responsible for facilitating communication and understanding between the parties, and for helping to resolve any conflicts that may arise. The term is derived from the Greek letters Sigma and Upsilon, which stand for 'MEDIATOR' and 'go-between' respectively. The term TAU (3 letters) is also related to this role, as it stands for 'TRUSTWORTHY'.