also: どし
noun, noun, used as a suffix
fellow; mutual; companion; comrade
Used as a suffix to indicate people sharing a common attribute, situation, or relationship. Also used as a standalone noun meaning 'fellows' or 'comrades'. The suffix use is very productive.
彼とは同士として長い付き合いだ。
He and I have been comrades for a long time.
同じ趣味を持つ同士で集まって、サークルを作った。
People who share the same hobby got together and formed a club.
隣同士で助け合うことが大切だ。
It's important for neighbors to help each other.