It is common in Japan for girls to confess their love to boys on St. Valentine’s Day by giving them chocolates. However, in America, not only married couples and lovers but also friends and family members verbally express their love to each other.
(j).
このタンパク質は細胞同士を結びつけるセメントのような役割をする。
This protein acts like cement in joining cells.
(k).
モンスター同士を戦わせるコンピュータゲームが間もなく発売される。
A computer game in which monsters fight against each other (literally: which makes monsters fight against each other) will be on sale soon.
Formation
Noun
同士
友達同士
The friends do something to/for each other/together