Brass is an alloy of copper and zinc. Copper usually makes up the larger share, while the zinc content is adjusted to change the alloy's colour, strength, hardness, ductility, and workability.
Unlike a pure chemical compound, brass does not have one fixed formula. Different brasses contain different proportions of copper and zinc, and some commercial grades include small amounts of lead, tin, aluminium, iron, manganese, silicon, or arsenic. These additions can improve machining, corrosion resistance, or strength.
Brass has a familiar yellow-gold appearance and is used for musical instruments, plumbing fittings, screws, locks, door hardware, radiators, ammunition casings, and decorative objects. Its acoustic properties help explain why instruments such as trumpets and trombones are commonly made from brass alloys.
The most common mix-up is with bronze. In the traditional distinction, brass is copper plus zinc, while bronze is primarily copper plus tin. Historical terminology was not always consistent, and some older objects described as brass may be broader copper alloys.