There is historical proof that Jeanne d’Arc had three ensigns… Two were for military use: her Battle Standard, which was large in size and her Pennon which was small. The third was a religious banner made for the priests and men of the army to assemble around for morning and evening prayers.
This excerpt contains four synonyms for flag: ensign, standard, pennon, and banner. English has many others.
In modern usage, an ensign is a country’s official national symbol, used to identify ships, airplanes, and official installations like military camps and embassies. This is the flag flown on patriotic occasions.
A pennon was a small flag, attached to a knight’s lance for identification. It was long, like a streamer, and usually triangular or swallow-tailed. A standard was larger and was fixed to a pole that could be stuck in the ground.
The word banner is often used for its emotional connotations, as in the U.S. national anthem:
O say, does that star-spangled banner yet wave
O’er the land of the free and the home of the brave.
In US usage, the flag is called an ensign when it is displayed on a vessel, the colors when carried by someone on foot, and a standard when displayed on a car or an aircraft, and by the cavalry.
Webster’s thesaurus gives the following flag synonyms, most of them not much used: banderole, banner, bannerol, burgee, color, ensign, gonfalon, gonfanon, jack, oriflamme, pendant, pennant, pennon, standard, streamer
A jack is the identifying flag flown on a ship. The Union Jack is the familiar British flag. When flown on land, it is properly called simply the “Union.” (See Wikipedia article for a differing view on the use of “Union Flag.”
The U.S. naval jack is the canton (the blue part with the stars) of the national ensign.
NOTE: The Union Jack began as the canton of a larger flag.
A burgee is a triangular pennant flown by members of yacht clubs. You can see a picture of one in the Wikipedia article on maritime flags.
The word oriflamme is familiar to readers of medieval history and romance. It was the sacred banner of the French kings, first mentioned in 1124.
In England, people turn out for the trooping of the colour, a patriotic parade held in June to celebrate the Queen’s birthday. U.S. military personnel on active service salute the colors twice a day: in the morning as the ensign is raised, and at sunset when it is lowered. In his unpleasant poem, “Ethiopia Saluting the Colors,” Walt Whitman uses a word not in Webster’s list, guidon, to refer to the cavalry flags carried by Sherman’s soldiers on their march to the sea.
The study of flags is called vexillology. The word comes from vexillum, Latin for flag.
You can find all sorts of fascinating vexillological information on the Flags of the World site.
For rules and regulations surrounding the U.S. flag, and some interesting violations thereof, visit the Betsy Ross flag site.