Bracket (noun)

1. A support attached to a wall or piece of furniture, typically one of two at either end of a shelf.
2. A device or part, especially one of a pair, used to clamp, fasten, or support something.
3. A mathematical symbol used to enclose numbers or expressions, especially to indicate that they are to be treated as a single unit.
4. A range of values, or a specific value or range, within which something is contained or classified.

Origin:

Late middle english (in the sense "supporting beam"): from old french braguette "leg armor", diminutive of brague "thigh", based on latin bracchium "arm".

Examples:

1. She put the vase on the bracket to keep it steady.
2. A bracket was fitted to the wall to support the shelves.
3. The values x + y and x - y are contained within the brackets.
4. His salary falls within the highest tax bracket.
5. The team was bracketed with the strongest contenders for the championship.