Best Friend Forever. 多经常用于女生之间的。
例如： We have so much in common, it‘s like you are my BFF.
Bro 哥们 Brother的缩写，commonly used in greetings,年轻男生之间
例如： Hey, he's my bro, I watch his back, and he watches mine, we're like brothers, yah know?
Friend Zone 备胎，好人卡
I spent all that money on a date, just to find out she put me in the Friend Zone.
FWB 床友 Friends With Benefits
英文释义：casual relationship implying no committment, but involving companionship
例如：she doesn't have a boyfriend, but she makes out with her FWB sometimes
side chick 小三
英文释义：a female that is neither a male's wife nor girlfriend but has relations with the male while he is in another relationship
Kimmy: Look at Tina and Josh...are they going out?
Sally: No Kimmy! Josh is dating Laura. Tina is just his sidechick.