Merge

A merge, or merged company, is a company that's fused from 2 other companies. They usually will have an appearance and personality that's a mix of the 2 companies.

Some companies stay merged forever after merging, others can merge and un-merge at will.

Merges
Square Enix

Bandai Namco - can un-merge back into Bandai and Namco, they usually stay in their unmerged form

Koei Tecmo