What is the meaning of “short selling” or “going short” a stock?
This is a gross simplification as there are a few different ways to do this. The principle overall is the same though. To short a stock, you borrow X shares from a third party and sell them at the current price. You now owe the lender X shares but have the proceeds from the sale. If the share price falls you can buy back those shares at the new lower price, return them to the lender and pocket the difference. The risk comes when the share price goes the other way, you now owe the lender the new value of the shares, so have to find some way to cover the difference. This happened a while back when Porsche made a fortune buying shares in Volkswagen from short sellers, and the price unexpectedly rose. Rich's answer captures the basic essence of short selling with example. I'd like to add these additional points: You typically need a specially-privileged brokerage account to perform short selling.  If you didn't request short selling when you opened your account, odds are good you don't have it, and that's good because it's not something most people should ever consider doing.  Short selling is an advanced trading strategy.  Be sure you truly grok selling short before doing it. Consider that when buying stock (a.k.a. going long or taking a long position, in contrast to short) then your potential loss as a buyer is limited (i.e. stock goes to zero) and your potential gain unlimited (stock keeps going up, if you're lucky!)   Whereas, with short selling, it's reversed: Your loss can be unlimited (stock keeps going up, if you're unlucky!) and your potential gain is limited (i.e. stock goes to zero.)   The proceeds you receive from a short sale – and then some – need to stay in your account to offset the short position.  Brokers require this.  Typically, margin equivalent to 150% the market value of the shares sold short must be maintained in the account while the short position is open. The owner of the borrowed shares is still expecting his dividends, if any.  You are responsible for covering the cost of those dividends out of your own pocket.  To close or cover your short position, you initiate a buy to cover.  This is simply a buy order with the intention that it will close out your matching short position.   You may be forced to cover your short position before you want to and when it is to your disadvantage!  Even if you have sufficient margin available to cover your short, there are cases when lenders need their shares back.  If too many short sellers are forced to close out positions at the same time, they push up demand for the stock, increasing price and deepening their losses.  When this happens, it's called a short squeeze. In the eyes of the public who mostly go long buying stock, short sellers are often reviled. However, some people and many short sellers believe they are providing balance to the market and preventing it sometimes from getting ahead of itself. [Disambiguation: A short sale in the stock market is not related to the real estate concept of a short sale, which is when a property owner sells his property for less than he owes the bank.] Additional references: The 'normal' series of events when trading a stock is to buy it, time passes, then you sell it. If you believe the stock will drop in price, you can reverse the order, selling shares, waiting for the price drop, then buying them back. During that time you own say, -100 shares, and are 'short' those shares. "The reason for selling a stock ""short"", is for when you believe the stock value will decrease in the near future. Here is an example: Today Exxon-Mobile stock is selling for $100 / share. You are expecting the price to decrease, so you want to short the stock, which means your broker (i.e. eTrade, etc) allows you to borrow shares without paying money, and those shares are transferred into your account, and then you sell them and receive money for the sale. But you didn't actually own those shares, you only borrowed them, so you need to return the shares to your broker sometime in the future.  Let's say you borrow 10 shares @ $100, and you sell them at the market price of $100, you receive $1,000 in your account. But you owe your broker 10 shares, which you need to return sometime in the future. A few days later, the share price has decreased to $80. Now you can buy 10 shares from the market at a total cost of $800. You get 10 shares, and return those shares to your broker. Since you originally took in $1,000, and you just paid out $800, you keep a resulting profit of $200"
"This doesn't make sense to me. Writing a covered call gives him a long delta position - the exact opposite of what he wants. And the tax losses won't turn a losing position into a winning one.  Is there something I'm missing?  Edit: Also, doesn't ""shorting against the box"" mean he has to have a long position, and short against that? That means you've got zero net delta, which isn't very useful at all..." One thing no one else has touched on is the issue of time frame. If I'm looking to hold my shares over the next few years, I don't mind riding out a few short-term bumps, while the short-seller is looking to make a quick profit on some bad news. Sure, I could sell and rebuy, but that's a lot of hassle, not to mention commissions and tax issues. "If you sell a stock you don't own, it's called a short sale. You borrowed the shares from an owner of the stock and eventually would buy to close. On most normal shares, you can hold a short position indefinitely, but there are some shares that have a combination of either a small float or too high a short position that shares to short are not available.  This can create a ""short squeeze"" where shorts are burned by being forced to buy the stock back.  Last - when you did this, you should have instructed the broker that you were ""selling to open"" or ""selling short."" In the old days, when people held stock certificates, you were required to send the certificate in when you sold. Today, the broker should know that wasn't your intention." The product type and transaction direction are not linked.  When you short sell a stock, you are still dealing with shares of an equity security.  When you take delivery of a bond, you are buying that bond and holding a long position even though it's a debt security. "I don't have anything definitive, but in general positions in a company are not affected materially by what is called a corporate action. ""Corp Actions"" can really be anything that affects the details of a stock. Common examples are a ticker change, or exchange change, IPO (ie a new ticker), doing a split, or merging with another ticker. All of these events do not change the total value of people's positions. If a stock splits, you might have more shares, but they are worth less per share. A merger is quite similar to a split. The old company's stock is converted two the new companies stock at some ratio (ie 10 shares become 1 share) and then converted 1-to-1 to the new symbol. Shorting a stock that splits is no different. You shorted 10 shares, but after the split those are now 100 shares, when you exit the position you have to deliver back 100 ""new"" shares, though dollar-for-dollar they are the same total value. I don't see why a merger would affect your short position. The only difference is you are now shorting a different company, so when you exit the position you'll have to deliver shares of the new company back to the brokerage where you ""borrowed"" the shares you shorted." In order to short a stock, you have to borrow the number of shares that you're shorting from someone else who holds the shares, so that you can deliver the shares you're shorting if it becomes necessary to do so (usually; there's also naked short selling, where you don't have to do this, but it's banned in a number of jurisdictions including the US). If a stock has poor liquidity, or is in high demand for shorting, then it may well be impossible to find anyone from whom it can be borrowed, which is what has happened in this instance. Matt Levine talked about a cute scam that this resembles, a kind of extended short squeeze. You manipulate up the stock of a company, so that it's obviously way above the fundamental value. Word will get out. Then the shorts come in. But the value remains stubbornly high. All the stock is held by a few insiders, but they didn't manipulate the stock price to do a pump and dump. They did it to milk the shorts on borrow cost. why can't I just use the same trick with my own shares to make money on the way    down? Because if you sell shares out of your own portfolio, by definition, you are not selling short at all. If you sell something you own (and deliver it) - then there is no short involved. A short is defined as a net negative position - i.e. you sell shares you do not have. Selling shares you own is selling shares you own - no short involved. You must borrow the shares for a short because in the stock market, you must DELIVER. You can not deliver shares you do not own. The stock market does not work on promises - the person who bought the shares expects ownership of them with all rights that gives them. So you borrow them to deliver them, then return them when you buy them back. "There are three ways to do this. So far the answers posted have only mentioned two.  The three ways are: Selling short means that you borrow stock from your broker and sell it with the intent of buying it back later to repay the loan.  As others have noted, this has unlimited potential losses and limited potential gains.  Your profit or loss will go $1:$1 with the movement of the price of the stock. Buying a put option gives you the right to sell the stock at a later date on a price that you choose now.  You pay a premium to have this right, and if the stock moves against you, you won't exercise your option and will lose the premium.  Options move non-linearly with the price of the stock, especially when the expiration is far in the future.  They probably are not for a beginner, although they can be powerful if used properly. The third option is a synthetic short position.  You form this by simultaneously buying a put option and selling short a call option, both at the same strike price.  This has a risk profile that is very much like the selling the stock short, but you can accomplish it entirely with stock options.  Because you're both buying an selling, in theory you might even collect a small net premium when you open. You might ask why you'd do this given that you could just sell the stock short, which certainly seems simpler.  One reason is that it is not always possible to sell the stock short.  Recall that you have to borrow shares from your broker to sell short.  When many people want to short the stock, brokers will run out of shares to loan.  The stock is then said to be ""hard to borrow,"" which effectively prevents further short selling of the stock.  In this case the synthetic short is still potentially possible." A bid is an offer to buy something on an order book, so for example you may post an offer to buy one share, at $5. An ask is an offer to sell something on an order book, at a set price. For example you may post an offer to sell shares at $6. A trade happens when there are bids/asks that overlap each other, or are at the same price, so there is always a spread of at least one of the smallest currency unit the exchange allows. Betting that the price of an asset will go down, traditionally by borrowing some of that asset and then selling it, hoping to buy it back at a lower price and pocket the difference (minus interest). So, let's say as per your example you borrow 100 shares of company 'X', expecting the price of them to go down. You take your shares to the market and sell them - you make a market sell order (a market 'ask'). This matches against a bid and you receive a price of $5 per share. Now, let's pretend that you change your mind and you think the price is going to go up, you instantly regret your decision. In order to pay back the shares, you now need to buy back your shares as $6 - which is the price off the ask offers on the order book. Because of this spread, you have lost money. You sold at a low price and bought at a high price, meaning it costs you more money to repay your borrowed shares. So, when you are shorting you need the spread to be as tight as possible. To short a stock you actually borrow shares and sell them. The shorter gets the money from selling immediately, and pays interest for the share he borrows until he covers the short. The amount of interest varies depending on the stock. It's typically under 1% a year for large cap stocks, but can be 20% or more for small, illiquid, or heavily shorted stocks. In this scam only a few people own the shares that are lent to shorters, so they essentially have a monopoly and can set really high borrow costs. The shorter probably assumes that a pump-and-dump will crash quickly, so wouldn't mind paying a high borrow cost. "Q: A: Everyone that is short is paying interest to the owners of the shares that the short seller borrowed. Although this quells your conundrum, this is also unrelated to the term. Interest in this context is just the number. In the options market, each contract also has an open interest, which tells you how many of that contract is being held. For your sake, think of it as ""how many are interested"", but really its just a completely different context." How so? If i sell short, then i make a profit only if the price goes down so i can buy back at a lower price. Yes, but if the price is going up then you would go long instead. Shorting a stock (or any other asset) allows you to profit when the price is going down. Going long allows you to profit when the price is going up. In the opposite cases, you lose money. In order to make a profit in either of those situations, you have to accurately assess which way the price will trade over the period of time you are dealing with. If you make the wrong judgment, then you lose money because you'll either sell for a lower price than you bought (if you went long), or have to buy back at a higher price than you sold for (if you went short). In either case, unless the trader can live with making a short-term loss and recouperating it later, one needs a good stop-loss strategy. Shorting is the term used when someone borrows a stock and sells it at the current price to then buy it back later at hopefully a lower price. There are rules about this as noted in the link that begins this answer as there are risks to selling a stock you don't own of course. If you look up various large companies you may find that there are millions of shares sold short throughout the market as someone does have the shares and they will need to be put back eventually. "No you don't have to be super-rich.  But... the companies do not have to sell you shares, and as others mention the government actively restricts and regulates the advertising and sales of shares, so how do you invest?  The easiest way to obtain a stake is to work at a pre-IPO company, preferably at a high level (e.g. Director/VP of under water basket weaving, or whatever).    You might be offered shares or options as part of a compensation package.  There are exemptions to the accredited investor rule for employees and a general exemption for a small number of unsolicited investors.  Also, the accredited investor rule is enforced against companies, not investors, and the trend is for investors to self-certify. The ""crime"" being defined is not investing in things the government thinks are too risky for you.  Instead, the ""crime"" being defined is offering shares to the public in a small business that is probably going to fail and might even be a scam from the beginning.   To invest your money in pre-IPO shares is on average a losing adventure, and it is easy to become irrationally optimistic.  The problem with these shares is that you can't sell them, and may not be able to sell them immediately when the company does have an IPO on NASDAQ or another market.  Even the executive options can have lock up clauses and it may be that only the founders and a few early investors make money."