option 的IV是甚麼?

An option is said to have intrinsic value if the option is in-the-money. When out-of-the money, its intrinsic value is zero.
The intrinsic value for an in-the-money option is calculated as the absolute value of the difference between the current price (S) of the underlying and the strike price (K) of the option, floored to zero.

IV = max{0, | S − K | }
More specifically, for a call option

IVcall = max{0,S − K}
while for a put option

IVput = max{0,K − S}
For example, if the stirke price for a call option is USD 1 and the price of the underlying is USD 1.20, then the option has an intrinsic value of USD 0.20.
The total value of an option is the sum of its intrinsic value and its time value.