How is a stop order price different from an ask price
Stop order is triggered when the market reaches the price you set. Until then - its not on the books. Your understanding is wrong in that you don't go to read the definition of the term.
Firstly what are you trading that you could lose more than you put in? If you are simply trading stocks you will not lose more than you put in, unless you are trading on margin. A limit order is basically that, a limit on the maximum price you want your buy order bought at or the minimum price you want your sell order sold at. If you can't be glued to the screen all day when you place a limit order, and the market moves the opposite way, you may miss out on your order being executed. Even if you can be in front of the screen all day, you then have to decide if you want to chase the market of miss out on your purchase or sale. For example, if a stock is trading at $10.10 and you put a limit buy order to buy 1000 shares at or below $10.00 and the price keeps moving up to $10.20, then $10.30 and then $10.50, until it closes the day at $11.00. You then have the choice during the day to miss out on buying the shares or to increase your limit order in order to buy at a higher price. Sometime if the stock is not very liquid, i.e. it does not trade very often and has low volume, the price may hit $10.00 and you may only have part of your order executed, say 500 out of your 1000 shares were bought. This may mean that you may have to increase the price of your remaining order or be happy with only buying 500 shares instead of 1000. The same can happen when you are selling (but in reverse obviously). With market order, however, you are placing a buy order to buy at the next bid price in the depth or a sell order to sell at the next offer price in the depth. See the market depth table below:  Note that this price depth table is taken before market open so it seems that the stock is somewhat illiquid with a large gap between the first and second prices in the buyers (bid) prices. When the market opened this gap is closed, as WBC is a major Australian bank and is quite liquid. (the table is for demonstration purposes only). If we pretend that the market was currently open and saw the current market depth for WBC as above, you could decide to place a limit sell order to sell 1000 shares at say $29.91. You would sell 100 shares straight away but your remaining 900 sell order will remain at the top of the Sellers list. If other Buyers come in at $29.91 you may get your whole sale completed, however, if no other Buyers place orders above $29.80 and other Sellers come into the market with sell orders below $29.91, your remaining order may never be executed. If instead you placed a market sell order you would immediately sell 100 shares at $29.91 and the remaining 900 shares at $29.80. (so you would be $99 or just over 0.3% worse off than if you were able to sell the full 1000 shares at $29.91). The question is how low would you have had to lower your limit order price if the price for WBC kept on falling and you had to sell that day? There are risks with whichever type of order you use. You need to determine what the purpose of your order is. Is it to get in or out of the market as soon as possible with the possibility of giving a little bit back to the market? Or is it to get the price you want no matter how long it takes you? That is you are willing to miss out on buying the shares (can miss out on a good buy if the price keeps rising for weeks or months or even years) or you are willing to miss out on selling them right now and can wait for the price to come back up to the price you were willing to sell at (where you may miss out on selling the shares at a good price and they keep on falling and you give back all your profits and more). Just before the onset of the GFC I sold some shares (which I had bought a few years earlier at $3.40) through a market order for $5.96. It had traded just above $6 a few days earlier, but if instead of a market order I had placed a limit order to sell at $6.00 or more I would have missed out on the sale. The price never went back up  to $6 or above, and the following week it started dropping very quickly. It is now trading at about $1.30 and has never gone back above $2.00 (5.5 years later). So to me placing a limit order in this case was very risky. It this a real situation or is it a made up example? Because for a stock that has a last traded priced of $5 or $6 and volume traded over $4M (i.e. it seems to be quite liquid), it is hardly likely that the difference from bid to ask would be as large as $1 (maybe for a stock that has volume of 4 to 5 thousand, but not for one having volume of 4 to 5 million). In regards to your question, if you were short selling the order would go in exactly the same as if you were selling a stock you owned. So your order would be on the ask side and would need to be matched up with a price on the bid side for there to be a trade. Stock price is determined by what's being asked for it, and what's being paid for it. The reported price is either a recent average, or is the last price at which a sale actually took place, depending on which you've asked for. Limit orders are an agreement between you and your brokerage, and have no direct effect on price. When and if their condition is triggered and the transaction takes place, the transaction is what's significant. "During the day, market and limit orders are submitted at any time by market participants and there is a bid and an ask that move around over time.  Trades occur whenever a market order is submitted or a limit order is submitted that at a price that matches or exceeds an existing limit order.  If you submit a market order, it may consume all best-price limit orders and you can get multiple prices, changing the bid or ask at the same time.  All that stuff happens during the trading day only. What happens at the end of the day is different.  A bunch of orders that were submitted during the day but marked as ""on close"" are aggregated with any outstanding limit orders to create a single closing price according to the algorithm established by the exchange.  Each exchange may handle the details of this closing event differently.  For example, the Nasdaq's closing cross or the NYSE's closing auction. The close is the most liquid time of the day, so investors who are trading large amounts and not interested in intraday swings will often submit a market-on-close or limit-on-close order.  This minimizes their chance of affecting the price or crossing a big spread.  It's actually most relevant for smaller stocks, which may have too little volume during the day to make big trades, but have plenty at the close.  In short, the volume you see is due to these on-close orders. The spike in volume most likely has no special information about what will happen overnight or the next day.  It's probably just a normal part of the market for illiquid stocks." "Price is decided by what shares are offered at what prices and who blinks first.  The buyer and seller are both trying to find the best offer, for their definition of best, within the constraints then have set on their bid or ask. The seller will sell to the highest bid they can get that they consider acceptable. The buyer will buy from the lowest offer they can get that they consider acceptable. The price -- and whether a sale/purchase happens at all -- depends on what other trades are still available and how long you're willing to wait for one you're happy with, and may be different on one share than another ""at the same time"" if the purchase couldn't be completed with the single best offer and had to buy from multiple offers. This may have been easier to understand in the days of open outcry pit trading, when you could see just how chaotic the process is... but it all boils down to a high-speed version of seeking the best deal in an old-fashioned marketplace where no prices are fixed and every sale requires (or at least offers the opportunity for) negotiation. ""Fred sells it five cents cheaper!"" ""Then why aren't you buying from him?"" ""He's out of stock."" ""Well, when I don't have any, my price is ten cents cheaper."" ""Maybe I won't buy today, or I'll buy elsewhere. ""Maybe I won't sell today. Or maybe someone else will pay my price. Sam looks interested..."" ""Ok, ok. I can offer two cents more."" ""Three. Sam looks really interested."" ""Two and a half, and throw in an apple for Susie."" ""Done."" And the next buyer or seller starts the whole process over again. Open outcry really is just a way of trying to shop around very, very, very fast, and electronic reconciliation speeds it up even more, but it's conceptually the same process -- either seller gets what they're asking, or they adjust and/or the buyer adjusts until they meet, or everyone agrees that there's no agreement and goes home." Stop order is shorter term for stop-loss order.  The point being that is intended as a protective measure.  A buy stop order would be used to limit losses when an investor has sold a stock short.  (Meaning that they have borrowed stock and sold it, in hopes that they can take advantage of a decline in the stock's price by replacing the borrowed stock later at a cheaper price.  The idea is to limit losses due to a rising stock price.)  Meanwhile, a sell stop order would be used to limit losses on a stock that an investor actually owns, by selling it before the price declines further. The important thing to keep in mind about stop orders is that they turn into market orders when the stop price is reached.  This means that they will be filled at the best available price when the order is actually executed.  In fast moving markets, this can be a price that is quite different from the stop price. A limit order allows an investor to ensure that they do not buy/sell a stock at more/less than the specified amount. The thing to keep in mind is that a limit order is not guaranteed to execute. A stop-limit order is a combination of a stop-loss order and limit order, in that it becomes a limit order (instead of a market order) when the stop price is reached. Links to definitions: Stop order Stop-limit order Limit order Market order What you have to remember is that Options are derivatives of another asset like stocks for example.  The price of the Option is derived from the price of the underlying. If the underlying is a stock for example, as the price of the stock moves up and down during the trading day, so will the Market Maker's fair value for the Option.  As Options are usually less liquid than the underlying stock, Market Makers are usually more active in 'Providing a Market' with Options. Thus if you place a limit order half way between the current Bid and Ask and the underlying stock price moves towards your limit order, the Market Maker will do their job and 'Provide a Market' at that price, thus executing your order. As others have stated, the current price is simply the last price at which the security traded. For any given tick, however, there are many bid-ask prices because securities can trade on multiple exchanges and between many agents on a single exchange. This is true for both types of exchanges that Chris mentioned in his answer. Chris' answer is pretty thorough in explaining how the two types of exchanges work, so I'll just add some minor details. In exchanges like NASDAQ, there are multiple market makers for most relatively liquid securities, which theoretically introduces competition between them and therefore lowers the bid-ask spreads that traders face. Although this results in the market makers earning less compensation for their risk, they hope to make up the difference by making the market for highly liquid securities. This could also result in your order filling, in pieces, at several different prices if your brokerage firm fills it through multiple market makers. Of course, if you place your order on an exchange where an electronic system fills it (the other type of exchange that Chris mentioned), this could happen anyway.  In short, if you place a market order for 1000 shares, it could be filled at several different prices, depending on volume, multiple bid-ask prices, etc. If you place a sizable order, your broker may fill it in pieces regardless to prevent you from moving the market. This is rarely a problem for small-time investors trading securities with high volumes, but for investors with higher capital like institutional investors, mutual funds, etc. who place large orders relative to the average volume, this could conceivably be a burden, both in the price difference across time as the order is placed and the increased bookkeeping it demands.  This is tangentially related, so I'll add it anyway. In cases like the one described above, all-or-none (AON) orders are one solution; these are orders that instruct the broker to only execute the order if it can be filled in a single transaction. Most brokers offer these, but there are some caveats that apply to them specifically. (I haven't been able to find some of this information, so some of this is from memory).  All-or-none orders are only an option if the order is for more than a certain numbers of shares. I think the minimum size is 300 or 400 shares.  Your order won't be placed until your broker places all other orders ahead of it that don't have special conditions attached to them.  I believe all-or-none orders are day orders, which means that if there wasn't enough supply to fill the order during the day, the order is cancelled at market close.  AON orders only apply to limit orders. If you want to replicate the behavior of a market order with AON characteristics, you can try setting a limit buy/sell order a few cents above/below the current market price. "Of the two, an option is a more reliable but more expensive means to get rid of a stock. As sdg said, a put option is basically an insurance policy on the stock; you pay a certain price for the contract itself, which locks in a sale price up to a particular future date. If the stock depreciates significantly, you exercise the option and get the contract price; otherwise you let the contract expire and keep the stock. Long-term, these are bad bets as each expired contract will offset earnings, but if you foresee a near-term steep drop in the stock price but aren't quite sure, a put option is good peace of mind. A sell stop order is generally cheaper, but less reliable. You set a trigger price, say a loss of 10% of the stock's current value. If that threshold is reached, the stop order becomes a sell order and the broker will sell the stock on the market, take his commission (or a fixed price depending on your broker) and you get the rest. However, there has to be a buyer willing to buy at that price at the moment the trigger fires; if a stock has lost 10% rapidly, it's probably on the way down hard, and the order might not complete until you realize a 12% loss, or a 15%, or even 20%. A sell stop limit (a combination stop order and limit order) allows you to say that you want to sell if the stock drops to $X, but not sell if it drops below $X-Y. This allows you to limit realized losses by determining a band within which it should be sold, and not to sell above or below that price. These are cheaper because you only pay for the order if it is executed successfully; if you never need it, it's free (or very cheap; some brokers will charge a token service fee to maintain a stop or stop limit). However, if the price drops very quickly or you specify too narrow a band, the stock can drop through that band too quickly to execute the sell order and you end up with a severely depreciated stock and an unexercised order. This can happen if the company whose stock you own buys another company; VERY quickly, both stocks will adjust, the buying company will often plummet inside a few seconds after news of the merger is announced, based on the steep drop in working capital and/or the infusion of a large amount of new stock in the buying company to cover the equity of the purchased company. You end up with devalued stock and a worthless option (but one company buying another is not usually reason to sell; if the purchase is a good idea, their stock will recover). Another option which may be useful to you is a swaption; this basically amounts to buying a put option on one financial instrument and a call on another, rolled into one option contract specifying a swap. This allows you to pick something you think would rise if your stock fell and exchange your stock for it at your option. For example, say the stock on which you buy this swaption is an airline stock, and you contract the option to swap for oil. If oil surges, the airline's stock will tank sharply, and you win both ways (avoiding loss and realizing a gain). You'd also win if either half of this option realized a gain over the option price; oil could surge or the airline could tank and you could win. You could even do this ""naked"" since its your option; if the airline's stock tanks, you buy it at the crashed price to exercise the option and then do so. The downside is a higher option cost; the seller will be no fool, so if your position appears to be likely, anyone who'd bet against you by selling you this option will want a pretty high return." At any point of time, buyer wants to purchase a stock at lesser price and seller wants to sell the stock at a higher price.  Let's consider this scenario  Company XYZ is trading at 100$, as stated above buyer wants to purchase at lower price and seller at higher price, this information will be available in Market depth, let's consider there are 5 buyers and 5 sellers, below are the details of their orders Buyers List Sellers List Highest order in buyers list will contain the bid price and bid quantity, Lowest order in Sellers list will contain the offer price and offer quantity. Now, if I want to buy 50 Stocks of company XYZ, need to place an order first, it can be either limit or Market. Limit Order : In this order, I will mention the price(buy price) at which I wish to buy, if there is any seller selling the stock less than or equal to price I have mentioned, then the order will be executed else it will be added to buyers list Market Order : In this order, I will not mention the price, if I wish to purchase 50 Stocks, then it will find the lowest offer price and buy stocks, in our case it will be 101. if I wish to purchase 200 Stocks, then it will find the lowest offer price and buy stocks, in our case it will be 2 transactions, since entire request cannot be accommodated in single order Usually the volume(Ask Volume and Offer Volume) being displayed are all Limit orders and not Market orders, Market orders are executed immediately. This is just an example, However several transactions are executed within a second, hence we will get to know the exact value only after the order is completed(executed) There could be a number of reasons: The price hit your number ($39.70) but by the time your order hit the market, the price had gone up. Perhaps the stock went up between when you placed the stop loss and when the order was executed. A trailing stop loss will ratchet up: Very simply, the trailing stop maintains a stop-loss order at a precise percentage below the market price (or above, in the case of a short position). The stop-loss order is adjusted continually based on fluctuations in the market price, always maintaining the same percentage below (or above) the market price. "Firstly, if a stock costs $50 this second, the bid/ask would have to be 49/50.  If the bid/ask were 49/51, the stock would cost $51 this second.  What you're likely referring to is the last trade, not the cost.  The last trading price is history and doesn't apply to future transactions. To make it simple, let's define a simple order book.  Say there is a bid to buy 100 at $49, 200 at $48, 500 at $47.  If you place a market order to sell 100 shares, it should all get filled at $49.  If you had placed a market order to sell 200 shares instead, half should get filled at $49 and half at $48.  This is, of course, assuming no one else places an order before you get yours submitted.  If someone beats you to the 100 share lot, then your order could get filled at lower than what you thought you'd get.  If your internet connection is slow or there is a lot of latency in the data from the exchange, then things like this could happen.  Also, there are many ECNs in addition to the exchanges which may have different order books.  There are also trades which, for some reason, get delayed and show up later in the ""time and sales"" window. But to answer the question of why someone would want to sell low... the only reason I could think is they desire to drive the price down." The company may have put a trading halt due to many reasons, most of the time it is because the company is about to release some news to the market. To stop speculation driving the price up or down, it puts a halt on trading until it can get all the information together and release it to the market. This could be news about an earnings update, a purchase of other businesses, a merger with another business, or a takeover bid, just to name a few. Rule 610 (Google for it) stands that if Bid and Ask are the same, the market is considered Locked, and the exchange must stop all trading. So the same person can't quote the same bid and ask price. However, HFTs have found ways to circumvent this limitation when exchanges created special order types for them, e.g. Spam-and-Cancel To whom is all this debt owed? I would imagine the US gov't, meaning we're really saying that the Federal government and US taxpayer are slowly easing into the role of subsidising post-secondary education, just as state governments fund primary and secondary (though without legislative or judicial action to make the added debt support explicit).  I thought most professors were supposed to be socialist anyway...you'd think they'd take on the needier students for free.