See the Wikipedia article ISO 216, the international standard on paper sizes.
- A standard paper size, defined by ISO 216 to have dimensions: 841 x 594 mm (840.90 x 594.60 mm)
- a sheet of A1 paper
From various rating systems, as that of Lloyd's of London or the condition of insured ships. First attested in 1837.
A1 (not comparable)
- (informal) In good health.
- (informal) In excellent or top condition.
- (of a ship) First-class. (Compare A 2 and A 3, which are inferior grades.)
- Under the International Union of Railways ("UIC") classification system, a steam locomotive that has two coupled driving wheels followed by two trailing wheels, with no leading wheels; also called an 0-2-2.