Why is a “long put” called long if you have a higher net position if the price decreases?
"Long here does not mean you wish for the underlying stock to increase in value, in fact, as the chart shows, just the opposite is true.  ""Long means you bought the derivative, and you own the option. The guy that sold it to you is at your mercy, he is short the put, and it's your decision to put the stock to him should it fall in value.  The value of the put itself rises with the falling stock price, you are long the put and want the put, itself, to rise in value." "You need to interpret ""security"" appropriately in Wikipedia's definition.  You should think of it as saying: to be long in a put, means the holder of the position owns the put   and will profit if the price of the put goes up And what makes the price of the put go up?  -- the price of the underlying stock going down."
"Simplest way to answer this is that on margin, one is using borrowed assets and thus there are strings that come with doing that. Thus, if the amount of equity left gets too low, the broker has a legal obligation to close the position which can be selling purchased shares or buying back borrowed shares depending on if this is a long or short position respectively. Investopedia has an example that they walk through as the call is where you are asked to either put in more money to the account or the position may be closed because the broker wants their money back. What is Maintenance Margin? A maintenance margin is the required   amount of securities an investor must hold in his account if he either   purchases shares on margin, or if he sells shares short. If an   investor's margin balance falls below the set maintenance margin, the   investor would then need to contribute additional funds to the account   or liquidate stocks in the account to bring the account back to the   initial margin requirement. This request is known as a margin call. As discussed previously, the Federal Reserve Board sets the initial   margin requirement (currently at 50%). The Federal Reserve Board also   sets the maintenance margin. The maintenance margin, the amount of   equity an investor needs to hold in his account if he buys stock on   margin or sells shares short, is 25%. Keep in mind, however, that this   25% level is the minimum level set, brokerage firms can increase, but   not decrease this level as they desire. Example: Determining when a margin call would occur. Assume that an   investor had purchased 500 shares of Newco's stock. The shares were   trading at $50 when the transaction was executed. The initial margin   requirement on the account was 70% and the maintenance margin is 30%.   Assume no transaction costs. Determine the price at which the investor   will receive a margin call. Answer: Calculate the price as follows: $50 (1- 0.70) = $21.43 1 - 0.30 A margin call would be received when the price of Newco's stock fell   below $21.43 per share. At that time, the investor would either need   to deposit additional funds or liquidate shares to satisfy the initial   margin requirement. Most people don't want ""Margin Calls"" but stocks may move in unexpected ways and this is where there are mechanisms to limit losses, especially for the brokerage firm that wants to make as much money as possible. Cancel what trade? No, the broker will close the position if the requirement isn't kept. Basically think of this as a way for the broker to get their money back if necessary while following federal rules. This would be selling in a long position or buying in a short sale situation. The Margin Investor walks through an example where an e-mail would be sent and if the requirement isn't met then the position gets exited as per the law." Consider the price history to be the sum of short term movements and long term movements. If you hold a stock for a long time you will benefit (or lose) from its long term movement.  If a sufficiently large and very good short term trader existed he would tend to reduce short term volatility, eventually to nearly zero. At that point, the price would rise gently over the course of the day in line with the long term variation in price. Presumably robot traders will increase the time horizon of their trades when they have exhausted the gains they can make from short term trades. It is known as the range or the price spread of the stock. You can read more about it here http://www.investopedia.com/terms/r/range.asp When volatility is higher, the option is more likely to end up in-the-money. Moreover, when it ends up in-the-money, it is likely to be over the strike price by a greater amount. Consider a call option. With high volatility, moves in the stock price are big - both up moves and down moves. If the stock moves up by a lot, the call option holder will benefit greatly. On the other hand, when the stock moves down, below a certain point the option holder does not care how big a down move the stock has. His downside is limited. Hence, the value of the option is increased by high volatility. I know everyone who searches this is looking for this answer. Bump so people are able to get this concept instead of looking all over the web for it. Just so I'm clear- the end result is a long call, and you think the stock is going up. There is nothing wrong with that fundamentally.  Be aware though: That's a negative theta trade. This means if your stock doesn't increase in price during the remaining time to expiration of your call option, the option will lose some of its value every day. It may still lose some of its value every day, depending on how much the stock price increases. The value of the call option just goes down and down as it approaches maturity, even if the stock price stays about the same. Being long a call (or a put) is a tough way to make money in the options market.  I would suggest using an out-of-the-money butterfly spread. The potential returns are a bit less. However, this is a cheap positive theta trade so you avoid time decay on the value of the option. "A lot of people have already explained that your assumptions are the issue, but I'll throw in my 2¢. There are a lot of people who do the opposite of long term investing.  It's called high frequency trading.  I'd recommend reading the Wikipedia article for more info, but very basically, high frequency traders use programs to determine which stocks to buy and which ones to sell. An example program might be ""buy if the stock is increasing and sell if I've held it more than 1 second.""" Something really does seem seedy that if I invest $2500, that I'll make above 50k if the stock doubles. Is it really that easy? You only buy or sell on margin. Think of when the stock moves in the opposite direction. You will loose 50k. You probably didn't look into that. Investment will vanish and then you will have debt to repay. Holding for long term in CFD accounts are charged per day. Charges depends on different service providers. CFD isn't and should not be used for long term. It is primarily for trading in the short term, maybe a week at the maximum. Have a look at the wikipedia entry and educate yourself. I would make a change to the answer from olchauvin: If you buy a call, that's because you expect that the value of call options will go up. So if you still think that options prices will go up, then a sell-off in the stock may be a good point to buy more calls for cheaper. It would be your call at that point (no pun intended). Here is some theory which may help. An options trader in a bank would say that the value of a call option can go up for two reasons: The VIX index is a measure of the levels of implied volatility, so you could intuitively say that when you trade options you are taking a view on two components: the underlying stock, and the level of the VIX index. Importantly, as you get closer to the expiry date this second effect diminishes: big jumps up in the VIX will produce smaller increases in the value of the call option. Taking this point to its limit, at maturity the value of the call option is only dependent on the price of the underlying stock. An options trader would say that the vega of a call option decreases as it gets closer to expiry. A consequence of this is that if pure options traders are naturally less inclined to buy and hold to expiry (because otherwise they would really just be taking a view on the stock price rather than the stock price & the implied volatility surface). Trading options without thinking too much about implied volatities is of course a valid strategy -- maybe you just use them because you will automatically have a mechanism which limits losses on your positions. But I am just trying to give you an impression of the bigger picture. Roll it into another put with a lower strike and hope it keeps going down.  At the very least it will defray the cost of the long position.  Ps I think you're looking for the word hedge not lever. "When you buy a put on a stock, you buy the right to sell the stock at fixed price, F, that his usually different from the market price, M. You paid a price, P, for the put.  Your potential profit, going forward, is represented by the DIFFERENCE you get to collect between your fixed price F, and that market price M, plus the price you paid for the put, or F-(M+P). (This assumes that F>(M+P). P is fixed, but the smaller M gets, the larger the term F-(M+P), and therefore the higher your potential profit from owning the put. So when M ""tanks,"" the put goes higher.  The $395 put is already in the money. If it were settled today, the value would be $395-$376 or $19. This, minus the cost of the put itself, represents your profit. The $365 put is ""out of the money."" The stock has to fall $11 more before the put is exercised. But if the stock went down 8 points today, that is less than the $19 difference at the start of the day. Because there is time between now and October, there is a chance for the stock to go down further, thereby going into the money. The current value of the put is represented by this ""chance."" Obviously, the chances of the stock going down $11 more (from today) is greater than the chance of it going down $19 more. On the other hand, the closer it gets to the expiration date, the less an out of the money put is worth. It's a race between the stock's fall, and the time to expiration." "Point of order: ""What goes up must come down"" refers to gravity of terrestrial objects below escape velocity and should not be generalized beyond its intent.  It's not true that stocks MUST come down just because they have gone up.  For example, we would not expecting the price of oil to come down to 1999 levels, right?  Prices, including those of stocks, are not necessarily cyclical. Anyway, short selling isn't necessarily a bad idea.  In some sense, it is insurance if you have a lot of assets (like maybe your human capital) that will take a dive when the market goes down.  Short selling would have lost a lot of money in your case as the stock market between 2011 (when you wrote the question) and 2014 (when I wrote this answer) performed very well.  On average the long side stock market should make money over long periods of time as compensation for risk and the short side should lose money, so it's not a good way to make money if you don't have an informational advantage.  Like all insurance, it protects you against certain calamities, but on average it costs you money." hmmm. I think it's because in both cases, you must pay for it up front, before the positions are closed out. You own nothing except the right to buy the stock re: the call, and the obligation to buy the stock re: the short.  You buy a call, but must borrow the stock, for which you must put some margin collateral and there is a cost to borrow. You pay for that, of course.  I wouldn't call it lending though. If it helps you to think about it, long is equivalent to betting for the upside and short is equivalent to betting for the downside. If you are long on options, then you expect the value of such options to increase.  If you are long an option, then you own the option.  If you are short an option, then generally you sold the option.  Someone who is short a call (sometimes called the writer or occasionally the issuer) has sold a call option to someone who is now long a call. Buying a call option that will increase in value is itself a form of investment, just as it's investment to buy stock or other instruments hoping they will appreciate in value.  An option's value will rise or fall with the underlying, so being long an option is a way to be long in the underlying.  Someone can be long in a stock by buying the stock, or long in a call by buying call options in the stock.  The long call generally requires less initial investment than buying the underlying, and lets the option-holder avoid the asset downside during the option term.  The risk is that the asset may not appreciate to the point that the call option will pay off. In the conceptual sense, a share of stock is a particular right to the profits and assets of a corporation, both in form of dividends and in liquidation.  An option is a particular right to the the share of stock.  It's just a further way to formalize and subdivide the various property rights that exist in a corporation.  If you can buy a piece of paper with particular rights to corporate profits and assets, then you can buy another piece of paper with particular rights to the former piece of paper. The mathematics make it easier to understand why this is the case. Using very bad shorthand, d1 and d2 are inputs into N(), and N() can be expressed as the probability of the expected value or the most probable value which in this case is the discounted expected stock price at expiration. d1 has two σs which is volatility in the numerator and one in the denominator.  Cancelling leaves one on top.  Calculating when it's infinity gives an N() of 1 for S and 0 for K, so the call is worth S and the put PV(K).  At 0 for σ, it's the opposite. More concise is that any mathematical moment be it variance which mostly influences volatility, mean which determines drift, or kurtosis which mostly influences skew are all uncertanties thus costs, so the higher they are, the higher the price of an option. Economically speaking, uncertainties are costs.  Since costs raise prices, and volatility is an uncertainty, volatility raises prices. It should be noted that BS assumes that prices are lognormally distributed.  They are not.  The closest distribution, currently, is the logVariance Gamma distribution. "A straddle is an options strategy in which one ""buys"" or ""sells"" options of the same maturity (expiry date) that allow the ""buyer"" or ""seller"" to profit based on how much the price of the underlying security moves, regardless of the direction of price movement. IE: A long straddle would be: You buy a call and a put at the same strike price and the same expiration date. Your profit would be if the underlying asset(the stock) moves far enough down or up(higher then the premiums you paid for the put + call options) (In case, one waits till expiry) Profit = Expiry Level - Strike Price - (Premium Paid for Bought Options) Straddle"