Bronze is an alloy made mainly of copper and tin.
Traditional bronze is primarily copper with tin added to change its mechanical properties. Many modern bronzes contain roughly 88% copper and 12% tin, although the proportions vary widely. Small additions of elements such as phosphorus, aluminum, manganese, nickel, zinc or silicon can improve strength, hardness, machinability or corrosion resistance.
Adding tin generally makes copper harder and more suitable for casting. Bronze alloys were especially important before iron became widespread because they could be shaped into tools, weapons, armor, vessels and ornaments. The archaeological period associated with their widespread use is therefore called the Bronze Age, which began at different times in different regions.
The most important neighboring distinction is bronze versus brass. Bronze traditionally uses tin as its characteristic secondary element, whereas brass is mainly copper and zinc. The terminology is not always perfect: historical objects can contain several metals, and museums may describe uncertain artifacts simply as copper alloys. “Bronze” also covers specialized materials such as aluminum bronze and phosphor bronze, but tin remains the standard answer to this basic composition question.