A binder can refer to different things depending on the context. Here are some possible meanings:

• Breast binder: Also known as chest binder, it is a piece of clothing that compresses breast tissue to reduce its appearance. It is commonly used by people with chest dysphoria, which is discomfort and distress from unwanted breast development. Binders can be made of spandex blends and cotton panels for comfort, and they can be worn beneath other clothing or on their own. However, they can also create health risks such as difficulty breathing, backache, skin rashes, and deformity of the ribs.

• Book binder: It is a person or machine that binds something, such as books. Binders can also refer to something used in binding, such as a detachable cover with clasps or rings for holding loose papers together.

In summary, a binder can be a piece of clothing used for breast binding or a tool used for bookbinding.