Noun+同士
Usage
X同士 indicates that Xs do something together, that Xs do something to/for/against each other, or that someone puts Xs together in some way. "Each other, between, among, together, with"
Examples
友達同士で話し合って決めてください。
Please discuss and decide among your friends.
このサイトでは、iPodのユーザー同士が意見を交換し合うこと事が出来ます。
On this site, iPod users can exchange opinions with each other.