An armband is a strip of cloth, plastic, or other material worn around the upper arm. Athletes often wear armbands to identify their team captain or to hold small items like music players. Swimmers might wear inflatable armbands that help them float while they're learning. Some workers wear reflective armbands at night so drivers can see them clearly.

In 1969, several American students wore black armbands to school to protest the Vietnam War. When the school suspended them, the case went all the way to the Supreme Court, which ruled that students don't lose their right to free speech just because they enter a school building. That case, Tinker v. Des Moines Independent Community School District, remains one of the most important decisions about student rights, showing how even something as simple as an armband can become powerful when it represents an idea.