- (paper size): Specified in ISO 216.
- (international standards) ISO 216 standard paper size of 594 mm × 841 mm (23.39 in × 33.11 in), with a surface area of 0.5 m2 (5.38 sq ft).
- (finance) Long-term bond credit rating by Moody's Investors Service, indicating that a bond is upper-medium grade with low risk of default.
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.)
A1 (plural A1s)
- 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.
See the Wikipedia article ISO 216, the international standard on paper sizes.
- A1 (a standard paper size, defined by ISO 216)
- “A-format” in Store norske leksikon