accession

1. A coming to; the act of acceding and becoming joined. (countable, uncountable) · a king's accession to a confederacy
2. Increase by something added; that which is added; augmentation from without. (countable, uncountable)
3. Such augmentation that adds to the collections of a museum or archive; a thing thus added. (countable, uncountable)
4. A mode of acquiring property, by which the owner of a corporeal substance which receives an addition by growth, or by labor, has a right to the part or thing added, or the improvement (provided the thing is not changed into a different species). (countable, uncountable)
5. The act by which one power becomes party to engagements already in force between other powers. (countable, uncountable) · accession to the European Union
6. The act of coming to or reaching a throne, an office, or dignity. (countable, uncountable) · her accession to the throne
7. The invasion, approach, or commencement of a disease; a fit or paroxysm. (countable, uncountable)
8. Agreement. (countable, uncountable)

Plural accessions