1. the act of formally joining or being admitted to a position, office, or organization
2. new items added to a collection, especially in a library or museum
Usage: library science; museum studies
3. the act of agreeing to or accepting a treaty, agreement, or proposal
Usage: formal; diplomatic

Examples

• The new king’s accession to the throne was celebrated nationwide.
• The library’s recent accessions include several rare manuscripts.
• The museum catalogued all new accessions from the donation.
• Several countries announced their accession to the climate agreement.
• The accession of new members strengthened the organization.
• Staff processed the monthly accessions for the archive.
• The treaty required formal accession by all participating nations.