Kate's Blog

These two words come by different routes from the same Latin source of our word accede.

In American English, accessory is dominant both as a noun and as an adjective, and it has fast become so now in British English,

although accessary is still used occasionally (where before it was used invariably) as a term in law in both varieties.

But -ory is preferable in all meanings:

As the one person who knew of their illegalities I felt I was becoming an accessory after the fact—S. Unwin, 1960

If he buried the captain, as he says, he's an accessory—R. Macdonald, 1971

Accessory ideas associated with the principal idea—M. Cohen, 1977.

An accessory role is played by another cellular enzyme—Health news release, American English 2005 [Old English (up to 1150)C].

As a noun, accessory has become widely used in the 20th century to refer to smaller articles of dress (gloves, handbag, etc.) or the extras in a motor vehicle (fog-lights, radio, etc.).

Accessories...may be considered essential to an outfit.—Alison Lurie, 1981.

Since September 11th, the emphasis has changed from using the flag as a fashion accessory to using it to show solidarity as a country—weblog, American English 2003 [Old English (up to 1150)C].

http://www.answers.com/topic/accessory