DEFINITION of 'Underlying Option Security'
An underlying option security is the financial instrument on which a derivative's (i.e., an option's) value is based – it provides the price that is used to determine the value of the derivative. An option is classified as a derivative because its value is derived from the underlying security.
BREAKING DOWN 'Underlying Option Security'
An option holder has the right, but not the obligation, to buy or sell a particular instrument at a specified price and date in the future.