Refers to a person or entity that has joined an organization, treaty, or agreement. Often used in formal contexts such as international treaties, business alliances, or membership-based groups.
The participants in this treaty number over 50 countries.
We are recruiting new members.
Compound of 加盟 (かめい, 'joining, affiliation') and 者 (しゃ, 'person'). The exact historical derivation is straightforward; the word follows standard Sino-Japanese compounding patterns.