Options basics: delta, calls, volatility, ITM and OTM

Question

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What do traders mean when they talk about delta, calls, volatility, and contracts being in the money or out of the money?

Short answer

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An option is a contract tied to an underlying asset, usually a stock or index. A call gives exposure to upside above a strike price, a put gives exposure to downside below a strike price, and terms like delta, implied volatility, in the money, and out of the money describe how sensitive that contract is and where it sits relative to the current market price.

Why this matters

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A lot of finance language is just compressed shorthand. If those basic terms are fuzzy, it is hard to understand what is actually being bought, what the real risk is, and why one option contract can behave very differently from another even on the same stock.

This is also where a lot of beginner mistakes start:

• confusing the price of the stock with the price of the option
• treating delta like a guaranteed probability
• talking about volatility without separating historical volatility from implied volatility
• assuming “cheap” options are cheap because they cost less in dollars

The basic building blocks

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Underlying

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The underlying is the asset the option is written on.

Examples:

• a stock like Apple
• an ETF like SPY
• an index

If someone says “the option on Tesla”, Tesla is the underlying.

Strike price

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The strike is the reference price built into the contract.

For a call, the strike is the price above which the contract starts to have intrinsic value.

For a put, the strike is the price below which the contract starts to have intrinsic value.

Expiration

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Every option has an expiration date. After that date, the contract is either exercised, expires worthless, or is closed before expiration.

Time matters because options are wasting assets. Even if your directional view is right, timing still matters.

Premium

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The premium is the price paid for the option.

If a call is quoted at 2.50, that is not usually 2.50 total. In equity options, one contract often controls 100 shares, so the premium is usually:

2.50 x 100 = 250

That is one of the first practical details beginners need to remember.

Calls and puts

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Call option

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A call generally gains value when the underlying goes up.

At a high level, buying a call is a bullish position:

• limited loss: the premium paid
• upside if the underlying rises enough

Example:

• stock price: 100
• call strike: 110

If the stock finishes well above 110, that call becomes more valuable.

Put option

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A put generally gains value when the underlying goes down.

Buying a put is a bearish position or a hedge:

• limited loss: the premium paid
• upside if the underlying falls enough

Example:

• stock price: 100
• put strike: 90

If the stock drops below 90, that put gains intrinsic value.

In the money, at the money, out of the money

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This is called moneyness. It describes where the strike sits relative to the current market price.

Call moneyness

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For a call:

• in the money (ITM): stock price is above the strike
• at the money (ATM): stock price is near the strike
• out of the money (OTM): stock price is below the strike

Example with stock at 100:

• 90 call: ITM
• 100 call: ATM
• 110 call: OTM

Put moneyness

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For a put:

• in the money (ITM): stock price is below the strike
• at the money (ATM): stock price is near the strike
• out of the money (OTM): stock price is above the strike

Example with stock at 100:

• 110 put: ITM
• 100 put: ATM
• 90 put: OTM

Why moneyness matters

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Moneyness affects:

• how much intrinsic value the option already has
• how much of the premium is pure time value
• how sensitive the option is to price moves and time decay

Not all options on the same underlying behave the same way. A deep ITM call and a far OTM call are very different instruments.

Intrinsic value and time value

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An option premium is usually thought of as:

option price = intrinsic value + time value

Intrinsic value

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This is the amount the option is already worth if exercised immediately.

For a call:

intrinsic value = max(stock price - strike, 0)

For a put:

intrinsic value = max(strike - stock price, 0)

Time value

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Everything above intrinsic value is time value.

That extra value exists because the option still has time to become more favorable before expiration.

Volatility

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Volatility is one of the most misunderstood words in options.

At a basic level, volatility is about how much the market expects the underlying to move.

Historical volatility

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This is based on how much the asset actually moved in the past.

Implied volatility

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This is backed out from current option prices. It reflects what the market is pricing in now.

When people talk about options being “expensive” or “cheap”, they are often talking about implied volatility, not the stock price itself.

Higher implied volatility usually means:

• higher option premiums
• more value in optionality
• more uncertainty being priced in

Lower implied volatility usually means:

• lower premiums
• less expected movement

A trader can be right on direction and still lose money if implied volatility collapses hard enough.

Delta

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Delta is the first Greek most people learn.

At a practical level, delta estimates how much the option price changes when the underlying moves by 1.

If a call has a delta of 0.40, that roughly means:

if the stock moves up by 1, the option price may move up by about 0.40

This is an approximation, not a fixed promise.

Delta for calls and puts

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• call deltas are usually positive
• put deltas are usually negative

That makes sense:

• calls generally benefit from the stock rising
• puts generally benefit from the stock falling

Delta and moneyness

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Delta also tends to vary with moneyness:

• deep OTM calls often have low delta
• ATM options often have medium delta
• deep ITM calls often have delta closer to 1

For puts, the same logic applies in the negative direction.

Delta is not the whole story

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Delta changes as the stock moves and as time passes. So it is useful, but incomplete.

That is why options traders eventually care about:

• gamma
• theta
• vega

But delta is the right place to start.

A simple example

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Assume:

• stock price: 100
• 1-month 105 call
• premium: 2.00
• delta: 0.35

This tells you a few things immediately:

• it is an OTM call because the strike is above the current stock price
• the contract costs about 200 if it controls 100 shares
• if the stock rises by 1, the option might gain about 0.35 in price, all else equal
• a lot of the premium is time value, because the call has no intrinsic value yet

That is already enough to reason about the contract more clearly than just saying “I bought a call.”

What would change the answer

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The exact behavior of an option depends on more than these definitions. A deeper explanation would need to add:

• the difference between buying and selling options
• American versus European exercise
• theta decay
• gamma and convexity
• vega and implied volatility changes
• assignment risk

But those are second-layer topics. The terms in this post are the foundation.

Closing thought

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The key mistake to avoid is treating options like simple leveraged stock. They are contracts with direction, time, and volatility all interacting at once.

If the vocabulary is clear, later questions become much easier:

• Is this option expensive?
• Is the market pricing in too much movement?
• Am I paying for time, intrinsic value, or both?
• Do I actually have the right view on direction and timing?

This post is educational only and not personalized financial advice.