noun

• (art) A picture or series of pictures painted on three tablets connected by hinges.
• (by extension) A group of three people or works, especially when considered representative of a particular field or theme.
• (film) A film or video sequence intended to be shown on a triple screen with the use of linked projectors.
• (philately) A set of three se-tenant postage stamps that form a composite picture.
• (figurative) Any set of three closely connected ideas or objects.