这个项目是一个三方合作，涉及三家公司。

This project is a ___three-way collaboration involving three companies.

他们讨论是否要尝试三人行的亲密关系。

They were discussing whether to try a ___threesome in their relationship.

这座桥有三个方向的分支，形成了一个三岔路口。

The bridge has a ___three-way split leading to different directions.