• 同盟どうめい — alliance
• 連盟れんめい — league; federation
• 加盟かめい — participation (in a league)
• 盟友めいゆう — ally; trusted partner
• 盟主めいしゅ — leader of an alliance
• 盟約めいやく — covenant; pledge

盟 combines 明 (bright/clear) and 皿 (dish/vessel), originally linked to rituals where an oath was sworn with offerings. It symbolizes a clear pledge or alliance made in front of others or the gods.

Today, it broadly refers to alliances, federations, and formal pledges among people or nations.