The security or property or loan agreement that an option gives the option holder the right to buy or to sell. Bloomberg Financial Dictionary
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The security, stock, commodity, index or future upon which an options or futures contract is based. Dresdner Kleinwort Wasserstein financial glossary
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The value of a derivative instrument depends on the performance of the underlying asset or security. These may be commodity derivatives such as gold, sugar, jute, pepper, iced broilers or coffee. They could also be financial in nature such as stocks, bonds, gilts, currencies and money market instruments. London Stock Exchange Glossary
Financial and business terms. 2012.