An armband is a piece of cloth worn around the arm over the sleeve of other clothing to mark the wearer as belonging to group, having a certain rank or role, or being in a particular state or condition.
When used as part of a military uniform it is called a brassard. Uniforms serving other purposes such as to identify members of clubs, societies or teams may also have armbands for certain ranks or functions. An armband might identify a group leader, a team captain, or a person charged with controlling or organizing an event.
In some cultures the wearing of a black armband signifies that the wearer is in mourning or wishes to identify with the commemoration of a comrade or team member who has died. This use is particularly common when a group or team meets after having lost a member. For further details of this use, see the topic on mourning.
The phrase to wear your heart on your sleeve, meaning to show your feelings, to display an emotional affiliation or conviction, is supposedly related to armbands. In medieval jousts, ladies of the court were said to tie a piece of cloth — a scarf or kerchief — around the arm of their favorite knight, who thus displayed his affection for the lady.