accession accession /ækˈsɛʃən/

noun

1. The act of attaining or gaining access to a new office or right or position (especially the throne)  ( accession , rise to power )
   the act of attaining or gaining access to a new office or right or position (especially the throne)
    Elizabeth's accession in 1558
   Elizabeth's accession in 1558
   
2. The right to enter  ( accession , admission , admittance , access , entree )
   the right to enter
   
3. Agreeing with or consenting to (often unwillingly)  ( accession , assenting )
   agreeing with or consenting to (often unwillingly)
    Accession to such demands would set a dangerous precedent
   accession to such demands would set a dangerous precedent
    Assenting to the Congressional determination
   assenting to the Congressional determination
   
4. Something added to what you already have  ( accession , addition )
   something added to what you already have
    The librarian shelved the new accessions
   the librarian shelved the new accessions
    He was a new addition to the staff
   he was a new addition to the staff
   
5. (civil law) the right to all of that which your property produces whether by growth or improvement  ( accession )
   (civil law) the right to all of that which your property produces whether by growth or improvement
   
6. A process of increasing by addition (as to a collection or group)  ( accession )
   a process of increasing by addition (as to a collection or group)
    The art collection grew through accession
   the art collection grew through accession
   

verb

1. (recording) make a record of additions to a collection, such as a library  ( accession )
   (recording) make a record of additions to a collection, such as a library