How to say "accession" in Japanese

• 登録とうろくJLPT N1approx.Common
  noun, suru verb, transitive verbReally 'registration' or 'entry': its 'accession' sense is the recording of new items in a register or record. For accession to a treaty or a throne, this is not the word you want.
  今いま登録とうろくされれば、１年間ねんかん無料むりょうです。↗

  Join now and pay nothing for a whole year.
• 継承けいしょうCommon
  noun, suru verb, transitive verbAccession here means succeeding to something — a throne, a title, an estate, or a position — taking it over from a predecessor; it also covers inheritance and the passing on of traditions.
  彼かれは王位おういを継承けいしょうすることになっていた。↗

  He was to succeed to the throne.
• 承継しょうけいCommon
  noun, suru verb, transitive verbSuccession and inheritance, especially the transfer of rights, duties, property, or a business from one party to another; near-synonymous with 継承, it is at home in legal and business contexts.
• 加盟かめいCommon
  noun, suru verb, intransitive verbAccession in the diplomatic sense: formally joining a treaty, convention, alliance, or organization and becoming a member party. When English 'accession' refers to joining an agreement, this is the word.
  加盟国かめいこく中ちゅう数カ国すうかこくは、Ｇ７の協定きょうていに従したがうことにあいまいな態度たいどを見みせています。↗

  Some member countries have been lax in abiding by G-7 agreements.

For accession to a treaty or organization use 加盟; for accession to a throne, office, or estate use 継承, with 承継 for legal and business succession; 登録 is really 'registration', fitting accession only as entry in a record.

Usage comparisons are AI-assisted and cross-checked by multiple models; for study reference only

• 登録とうろくregistration
• 継承けいしょうinheritance
• 承継しょうけいsuccession
• 加盟かめいjoining (an association, agreement, etc.)
• 付合ふごうaccession
• 践祚せんそaccession (to the throne)
• 登極とうきょく(Imperial) accession