meaning - Difference between "banner" and "flag"

What's the difference between the meaning of "banner" and the meaning of "flag"?

Answer

While the two terms are sometimes interchangeable, I would say that the usage would differ depending on the shape and purpose of the item in question.

A flag would typically be square or slightly oblong, as with the national flags of most countries. A banner tends to be more elongated, for example as you might see hung across a street during a parade. Flags tend to be attached by one side to a pole, whereas banners are typically attached at both ends, either fixed or on two poles. Furthermore, flags usually carry representative symbols or colours (e.g., chequered flag), whereas banners generally carry written messages (e.g., Happy Birthday Joe!)

On this basis few English speakers would refer to, say, the Union Jack as a banner. Likewise, Happy Birthday Joe! would not be called a flag.