Moneyness
Moneyness describes where an option's strike price sits relative to the underlying's current price — in the money, at the money, or out of the money.
What it is
Moneyness is a label for the relationship between an option's strike price (the fixed price written into the contract) and the current market price of the underlying asset. A call option is in the money when the underlying trades above the strike and out of the money when it trades below; a put option is the reverse, in the money when the underlying trades below the strike. At the money means the strike sits at or very near the current price. Moneyness indicates only whether intrinsic value — what exercising the contract right now would be worth — is positive or zero. It says nothing about what the contract cost, so an in-the-money label is not a statement that the position is profitable.
Why it matters
Moneyness is the quickest way to classify an option contract, and it maps onto the split between intrinsic value (the in-the-money amount, which is zero for any out-of-the-money contract) and time value (the option's current market price minus its current intrinsic value). An out-of-the-money option has no intrinsic value: its entire price is time value, and if the underlying never moves past the strike the contract expires worthless and the buyer loses 100% of the premium — a total loss on that contract. Moneyness also tracks roughly with sensitivity to the underlying: deep in-the-money contracts move nearly dollar-for-dollar with it, calls in the same direction and puts in the opposite, while far out-of-the-money contracts barely respond. Moneyness also drives whether a writer gets assigned, and an uncovered call writer's loss is theoretically unlimited.
How it's calculated
Moneyness is read off two numbers rather than modelled: the strike written into the contract, and the current market price (spot) of the underlying. For a call, spot above strike is in the money; for a put, spot below strike is in the money; equal or near-equal is at the money. The dollar depth is intrinsic value: max(spot − strike, 0) for a call, max(strike − spot, 0) for a put — never negative, because the holder is never obliged to exercise a losing option (the writer, by contrast, must perform if assigned). Moneyness is also stated as a ratio — spot ÷ strike for a call, strike ÷ spot for a put, so above 1 is in the money either way — or as a percentage distance from the strike.