"Four people as a group" can be referred to as "a quartet" in Engpsh.
The term "quartet" comes from the musical term meaning a group of four musicians playing together, and it has been extended to other groups of four people.
Example sentences:
The quartet of friends went on a camping trip together.
四人一组的朋友一起去野营。
The famous string quartet will perform at the concert tonight.
著名的四重奏乐队今晚将在音乐会上表演。
The company is divided into several quartets to work on different projects.
公司分为几个四人一组的小组，分别处理不同的项目。