See the Wikipedia article w:ISO 216|ISO 216, the international standard on paper sizes.
- A standard paper size, defined by ISO 216.
#: dimensions: 841 x 594 mm (840.90 x 594.60 mm)
- of that size
#: a sheet of A1 paper
- In good health. Derived from "A-1 at Lloyd's", an old marine insurance phrase, referring to Wikipedia:Lloyd's of London|Lloyd's of London insurance company registering first-class ships as A-1.
- A major thoroughfare in England
#: You should take the A1 north from Newcastle.
- Under the w:International Union of Railways|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.