A metallic material composed of two or more elements intimately mixed, usually in the molten state. There are a few naturally-occurring alloys, such as 'electrum': a mixture of silver and gold. Bronze, brass, pewter and spelter are all man-made alloys. The nomenclature of alloys follows no definite rules, the name or names given to an alloy or group of alloys usually bear no relation whatever to the metals involved. An alloy of two metals is called a 'binary alloy'; an alloy of three metals a 'ternary alloy'. There are several thousand commercially used alloy specifications. Metals are alloyed in order to enhance such properties as hardness, corrosion resistance, strength or workability, raise or lower melting point and create varying colours. Economics may also play a part, if cost can be reduced by alloying, using a smaller proportion of an expensive metal to achieve the required performance.