Underlying stock

[Renato]

(FINANCE) a stock whose price movements determine the value of a [financial derivative]. For example, when a hedge fund manager writes a [call option] for Citigroup ([NYSE]:C) at 4.25/share, C is the underlying stock.
Underlying can be used to refer to other things besides stocks; for example, commodities, currencies, or bonds.

[Agnes]

→  underlying shares