PLAIN-LANGUAGE DEFINITION
Thumbnail
A thumbnail is a small preview image used to represent a piece of content.
IN PRACTICE
An example
A clear product-and-action frame can help identify a demonstration in a grid.
What this does not tell you
A compelling preview should still accurately represent the content.
Use the term precisely
When you use this term in a brief or report, include the relevant source, scope and assumptions. An example explains the concept; it is not a benchmark or a promise of results.