Noun

1. A standard paper size, defined by ISO 216.

   dimensions: 210 x 297 mm

Quotations

• 2001 — Eoin Colfer, Artemis Fowl, p 66

  "There are preparations to be made for our guest's arrival," said Artemis, handing a typewritten sheet of A4 to Juliet.

Noun

1. one in a series of alphanumerics used in many national road systems.

   The A4, which runs from London to Bristol, used to be known as the Great West Road.