See the Wikipedia article ISO 216, the international standard on paper sizes.
- A standard paper size, defined by ISO 216.
- dimensions: 420 x 297 mm (420.448 x 297.302 mm)
- (countable, management) A one-page document, often tabular or graphical, on such paper.
- (UK, rail transport) A3 class, a class of steam locomotive used on the London and North Eastern Railway.