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joining (an association, agreement, etc.); participation; affiliation; accession
新たな国が国際機関に加盟した。
A new country joined the international organization.
加盟国の数は年々増え続けている。
The number of member states continues to grow year by year.
加盟に必要な条件を全て満たした。
All the conditions required for membership were met.