悪友[akuyuu] undesirable friend
畏友[iyuu] one's esteemed friend
益友[ekiyuu] good friend
学友[gakuyuu] school friend
級友[kyuuyuu] classmate

旧友[kyuuyuu] crony
血友病[ketsuyuubyou] haemophilia
交友[kouyuu] friend
交友関係[kouyuukankei] one's relationships
校友[kouyuu] schoolmate

加盟[kamei] participation
加盟国[kameikoku] member-nation
加盟者[kameisha] participants
加盟店[kameiten] participating store
軍事同盟[gunjidoumei] military alliance

三国同盟[sangokudoumei] triple alliance
盟う[chikau] to swear
同盟休校[doumeikyuukou] student strike
同盟軍[doumeigun] allied armies
同盟国[doumeikoku] ally (of another nation)