TWAIN is an interface that enables applications to transmit images from imaging hardware devices. These devices primarily include digital cameras and page scanners. Images when acquired are scanned directly into the application for direct manipulation.

TWAIN support is a term for the client application. Applications which conform to the TWAIN interface and acquire images into their application are said to have TWAIN support. A data source which complies with the TWAIN interface is said to be TWAIN-compliant.

TWAIN is not an acronym. The word TWAIN is from Kipling's, "The Ballad of East and West" - "...and never the twain shall meet." However, many people believe that it is indeed an acronym. Perhaps the best entry for an acronym was "Technology Without An Interesting Name."

Nearly every application that supports some form of photo-identification will benefit by including TWAIN support with their application. A health club that has photo-ID for its members or a hospital and employee identification tags. Even things as simple as a plant collection, fish database, and coin collections can benefit by having the ability to scan images into a table.