Artwork Classification Terms (from Artsy.com)

Unique: One of a kind piece, created by the artist. 

Limited Edition: Original works created in multiple with direct involvement of the artist. Generally, editions are smaller than 150 pieces total. 

Made-to-Order: A piece that is made-to-order, taking into account the collector's preferences. 

Reproduction: Reproduction of an original work authorized by the artist's studio or estate. The artist was not directly involved in the production of this work. 

Editioned Multiple: Pieces created in larger limited editions, authorized by the artist's studio or estate. These works are not produced with direct involvement of the artist. 

Non-Editioned Multiple: Works made in unlimited or unknown numbers of copies, authorized by the artist's studio or estate. These works are not produced with direct involvement of the artist. 

Ephemera: Items related to the artist, created or manufactured for a specific, limited use. This includes exhibition materials, memorabilia, autographs, etc.