In heraldry, azure (/ˈæʒər/, /ˈæʒʊər/ or /ˈeɪʒər/) is the tincture with the colour blue, and belongs to the class of tinctures called "colours". In engraving, it is sometimes depicted as a region of horizontal lines or else is marked with either az. or b. as an abbreviation.
The term azure derives from the name of the deep blue stone now called lapis lazuli (stone of Lazhward). The word was adopted into Old French by the 12th century, after which the word passed into use in the blazon of coats of arms.
As an heraldic colour, the word azure simply means "blue". It is one of many concepts with both a French and Germanic word in English, the former being used by the French-speaking nobles following the Norman Conquest of England in 1066 and the latter being used by the commoners of Anglo-Saxon stock. So while French-speaking heralds described banners as azure, commoners simply called them blue. Because it comes from a French word that simply means "blue", a wide range of colour values is used in the depiction of azure in armory and flags.