Accession \Ac*ces"sion\, n. [L. accessio, fr. accedere: cf. F. accession. See Accede.]

1. A coming to; the act of acceding and becoming joined; as, a king's accession to a confederacy.

2. Increase by something added; that which is added; augmentation from without; as, an accession of wealth or territory.

The only accession which the Roman empire received was the province of Britain. --Gibbon.

3. (Law)
   (a) 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). Thus, the owner of a cow becomes the owner of her calf.
   (b) The act by which one power becomes party to engagements already in force between other powers. --Kent.

4. The act of coming to or reaching a throne, an office, or dignity; as, the accession of the house of Stuart; -- applied especially to the epoch of a new dynasty.

5. (Med.) The invasion, approach, or commencement of a disease; a fit or paroxysm.

Syn: Increase; addition; augmentation; enlargement.

Source: Webster's Revised Unabridged Dictionary (1913)