implied volatility for upside (i.e. high strike) equity options is typically lower than for at-the-money equity options. However, the implied volatilities of options on foreign exchange contracts tend to rise in both the downside and upside directions. In equity markets, a small tilted smile is often observed near the money as a kink in the general downward sloping implicit volatility graph. Sometimes the term "smirk" is used to describe a skewed smile. Market practitioners use the term implied-volatility to indicate the volatility parameter for ATM (at-the-money) option. Adjustments to this value are undertaken by incorporating the values of Risk Reversal and Flys (Skews) to determine the actual volatility measure that may be used for options with a delta which is not 50. Formula where: is the implied volatility at which the x%-delta call is trading in the market is the implied volatility of the x%-delta put ATM is the At-The-Money Forward vol at which ATM Calls and Puts are trading in the market Risk reversals are generally quoted as x% delta risk reversal and essentially is Long x% delta call, and short x% delta put. Butterfly, on the other hand, is a strategy consisting of: −y% delta fly which mean Long y% delta call, Long y% delta put, short one ATM call and short one ATM put (small hat shape). Implied volatility and historical volatility It is helpful to note that implied volatility is related to historical volatility, but the two are distinct. Historical volatility is a direct measure of the movement of the underlying’s price (realized volatility) over recent history (e.g. a trailing 21-day period). Implied volatility, in contrast, is determined by the market price of the derivative contract itself, and not the underlying. Therefore, different derivative contracts on the same underlying have different implied volatilities as a function of their own supply and demand dynamics. For instance, the IBM call option, strike at $100 and expiring in 6 months, may have an implied volatility of 18%, while the put option strike at $105 and expiring in 1 month may have an implied volatility of 21%. At the same time, the historical volatility for IBM for the previous 21 day period might be 17% (all volatilities are expressed in annualized percentage moves). Term structure of volatility For options of different maturities, we also see characteristic differences in implied volatility. However, in this case, the dominant effect is related to