Transparency
From The Glossary of Digital Photography
(1) An object that allows light to pass through it. The object is thus clear and not merely translucent. (2) In analog photography, a piece of transparent film that shows a positive version of an image. The most common transparency is a color positive, which can range in size from a 35mm transparency (also called a slide) up to an 8 x 10 inch positive image. See also translucent
