Risk of buying stock
I'd recommend investing in a mutual fund that diversifies your purchase across a number of stocks (and bonds, depending on the fund). Vanguard has some of the lowest fees around, and have a large number of funds to choose from. Take a look at their offerings for a data point if nothing else. If you buy stock in established companies, it is vey unlikely that they will lose all their value. Spreading your money across multiple stocks -- diversifying -- reduces that risk because it is extremely unlikely that they all lose all their value at once. Spreading them across multiple industries and adding bonds to the mix increases diversification. Of course the trade-off is that if one of the stocks skyrockets you don't benefit as much as if you had been lucky enough to put all your money in that one stock.  You need to decide for yourself how much risk you are willing to tolerate in exchange for the chance of gains.  Other answers on this site have dealt with this in more detail. When you buy shares, you are literally buying a share of the company.  You become a part-owner of it. Companies are not required to pay dividends in any given year.  It's up to them to decide each year how much to pay out. The value of the shares goes up and down depending on how much the markets consider the company is worth.  If the company is successful, the price of the shares goes up.  If it's unsuccessful, the price goes down.  You have no control over that.  If the company fails completely and goes bankrupt, then the shares are worthless. Dilution is where the company decides to sell more shares.  If they are being sold at market value, then you haven't really lost anything.  But if they are sold below cost (perhaps as an incentive to certain staff), then the value of the company per share is now less.  So your shares may be worth a bit less than they were.  You would get to vote at the AGM on such schemes.  But unless you own a significant proportion of the shares in the company, your vote will probably make no difference. In practice, you can't protect yourself.  Buying shares is a gamble.  All you can do is decide what to gamble on.
This is a very good question! The biggest difference is that when you put money in a savings bank you are a lender that is protected by the government, and when you buy stocks you become an owner. As a lender, whether the bank makes or loses money on the loans it makes, they still maintain your balance and pay you interest, and your principal balance is guaranteed by the government (in the USA). The bank is the party that is primarily at risk if their business does not perform well. As an owner, you participate fully in the company's gains and losses, but you also put your money at risk, since if the company loses money, you do too. Because of this, many people prefer to buy funds made up of many stocks, so they are not at risk of one company performing very poorly or going bankrupt. When you buy stock you become a part owner and share in the profitability of the company, often through a dividend. You should also be aware that stocks often have years where they do very poorly as well as years when they do very well. However, over a long period of time (10 years or more), they have historically done better in outpacing inflation than any other type of investment. For this reason, I would recommend that you only invest in the stock market if you expect to be able to leave the money there for 10 years or more, ideally, and for 5 years at the very least. Otherwise, you may need to take the money out at a bad time. I would also recommend that you only invest in stocks if you already have an emergency fund, and don't have consumer debt. There isn't much point in putting your money at risk to get a return if you can get a risk-free return by paying off debt, or if you would have to pull your money back out if your car broke down or you lost your job. Say I am an employee of Facebook and I will be able to sell stares at enough of a profit to pay of my mortgage and have enough money left to cover my living costs for many years. I also believe that there is a 95% chance that the stock price will go up in the next few years. Do I take a 5% risk, when I can transform my life without taking any risk?   (The USA tax system as explained by JoeTaxpayer increases the risk.)  So you have a person being very logical and selling stocks that they believe will go up in value by more than any other investment they could have.   It is called risk control. (Lot of people will know the above; therefore some people will delay buying stock until Lock Up expiration day hoping the price will be lower on that day.   So the price may not go down.) When you buy a stock, the worst case scenario is that it drops to 0.  Therefore, the most you can lose when buying a stock is 100% of your investment. When you short a stock, however, there's no limit on how high the stock can go.  If you short a stock at 10, and it goes up to 30, then you've lost 200% on your investment.  Therefore shorting stocks is riskier than buying stocks, since you can lose more than 100% of your investment when shorting. because the price might go up, but it will never be as big of a change as a regular price drop i suppose... That is not true.  Stocks can sometimes go up significantly (50-100% or more) in a very short amount of time on a positive news release (such as an earnings or a buyout announcement).  A famous example occurred in 2008, when Volkswagen stock quintupled (went up 400%) in less than 2 days on some corporate news: Porsche, for some reason, wants to control Volkswagen, and by building up its stake has driven up the price. Hedge funds, figuring the share price would fall as soon as Porsche got control and stopped buying, sold a lot of VW shares short. Then last weekend, Porsche disclosed that it owned 42.6 percent of the stock and had acquired options for another 31.5 percent. It said it wanted to go to 75 percent. The result: instant short-squeeze. The German state of Lower Saxony owns a 20 percent stake in VW, which it said it would not sell. That left precious few shares available for anyone else. The shorts scrambled to cover, and the price leaped from about €200, or about $265, to above €1,000. "This is an old post I feel requires some more love for completeness.  Though several responses have mentioned the inherent risks that currency speculation, leverage, and frequent trading of stocks or currencies bring about, more information, and possibly a combination of answers, is necessary to fully answer this question. My answer should probably not be the answer, just some additional information to help aid your (and others') decision(s). Firstly, as a retail investor, don't trade forex. Period. Major currency pairs arguably make up the most efficient market in the world, and as a layman, that puts you at a severe disadvantage. You mentioned you were a student—since you have something else to do other than trade currencies, implicitly you cannot spend all of your time researching, monitoring, and investigating the various (infinite) drivers of currency return. Since major financial institutions such as banks, broker-dealers, hedge-funds, brokerages, inter-dealer-brokers, mutual funds, ETF companies, etc..., do have highly intelligent people researching, monitoring, and investigating the various drivers of currency return at all times, you're unlikely to win against the opposing trader. Not impossible to win, just improbable; over time, that probability will rob you clean. Secondly, investing in individual businesses can be a worthwhile endeavor and, especially as a young student, one that could pay dividends (pun intended!) for a very long time. That being said, what I mentioned above also holds true for many large-capitalization equities—there are thousands, maybe millions, of very intelligent people who do nothing other than research a few individual stocks and are often paid quite handsomely to do so. As with forex, you will often be at a severe informational disadvantage when trading. So, view any purchase of a stock as a very long-term commitment—at least five years. And if you're going to invest in a stock, you must review the company's financial history—that means poring through 10-K/Q for several years (I typically examine a minimum ten years of financial statements) and reading the notes to the financial statements. Read the yearly MD&A (quarterly is usually too volatile to be useful for long term investors) – management discussion and analysis – but remember, management pays themselves with your money. I assure you: management will always place a cherry on top, even if that cherry does not exist. If you are a shareholder, any expense the company pays is partially an expense of yours—never forget that no matter how small a position, you have partial ownership of the business in which you're invested. Thirdly, I need to address the stark contrast and often (but not always!) deep conflict between the concepts of investment and speculation. According to Seth Klarman, written on page 21 in his famous Margin of Safety, ""both investments and speculations can be bought and sold. Both typically fluctuate in price and can thus appear to generate investment returns. But there is one critical difference: investments throw off cash flow for the benefit of the owners; speculations do not. The return to the owners of speculations depends exclusively on the vagaries of the resale market."" This seems simple and it is; but do not underestimate the profound distinction Mr. Klarman makes here. (and ask yourself—will forex pay you cash flows while you have a position on?) A simple litmus test prior to purchasing a stock might help to differentiate between investment and speculation: at what price are you willing to sell, and why? I typically require the answer to be at least 50% higher than the current salable price (so that I have a margin of safety) and that I will never sell unless there is a material operating change, accounting fraud, or more generally, regime change within the industry in which my company operates. Furthermore, I then research what types of operating changes will alter my opinion and how severe they need to be prior to a liquidation. I then write this in a journal to keep myself honest. This is the personal aspect to investing, the kind of thing you learn only by doing yourself—and it takes a lifetime to master. You can try various methodologies (there are tons of books) but overall just be cautious. Money lost does not return on its own. I've just scratched the surface of a 200,000 page investing book you need to read if you'd like to do this professionally or as a hobbyist. If this seems like too much or you want to wait until you've more time to research, consider index investing strategies (I won't delve into these here).  And because I'm an investment professional: please do not interpret anything you've read here as personal advice or as a solicitation to buy or sell any securities or types of securities, whatsoever. This has been provided for general informational purposes only. Contact a financial advisor to review your personal circumstances such as time horizon, risk tolerance, liquidity needs, and asset allocation strategies. Again, nothing written herein should be construed as individual advice." The catch is that you're doing a form of leveraged investing. In other words, you're gambling on the stock market using money that you've borrowed. While it's not as dangerous as say, getting money from a loan shark to play blackjack in Vegas, there is always the chance that markets can collapse and your investment's value will drop rapidly. The amount of risk really depends on what specific investments you choose and how diversified they are - if you buy only Canadian stocks then you're at risk of losing a lot if something happened to our economy. But if your Canadian equities only amount to 3.6% of your total (which is Canada's share of the world market), and you're holding stocks in many different countries then the diversification will reduce your overall risk.  The reason I mention that is because many people using the Smith Maneuver are only buying Canadian high-yield dividend stocks, so that they can use the dividends to accelerate the Smith Maneuver process (use the dividends to pay down the mortgage, then borrow more and invest it). They prefer Canadian equities because of preferential tax treatment of the dividend income (in non-registered accounts). But if something happened to those Canadian companies, they stand to lose much of the investment value and suddenly they have the extra debt (the amount borrowed from a HELOC, or from a re-advanceable mortgage) without enough value in the investments to offset it. This could mean that they will not be able to pay off the mortgage by the time they retire! "Yes, you're still exposed to currency risk when you purchase the stock on company B's exchange. I'm assuming you're buying the shares on B's stock exchange through an ADR, GDR, or similar instrument. The risk occurs as a result of the process through which the ADR is created. In its simplest form, the process works like this: I'll illustrate this with an example. I've separated the conversion rate into the exchange rate and a generic ""ADR conversion rate"" which includes all other factors the bank takes into account when deciding how many ADR shares to sell. The fact that the units line up is a nice check to make sure the calculation is logically correct. My example starts with these assumptions: I made up the generic ADR conversion rate; it will remain constant throughout this example. This is the simplified version of the calculation of the ADR share price from the European share price:  Let's assume that the euro appreciates against the US dollar, and is now worth 1.4 USD (this is a major appreciation, but it makes a good example):  The currency appreciation alone raised the share price of the ADR, even though the price of the share on the European exchange was unchanged. Now let's look at what happens if the euro appreciates further to 1.5 USD/EUR, but the company's share price on the European exchange falls:  Even though the euro appreciated, the decline in the share price on the European exchange offset the currency risk in this case, leaving the ADR's share price on the US exchange unchanged. Finally, what happens if the euro experiences a major depreciation and the company's share price decreases significantly in the European market? This is a realistic situation that has occurred several times during the European sovereign debt crisis.   Assuming this occurred immediately after the first example, European shareholders in the company experienced a (43.50 - 50) / 50 = -13% return, but American holders of the ADR experienced a (15.95 - 21.5093) / 21.5093 = -25.9% return. The currency shock was the primary cause of this magnified loss.  Another point to keep in mind is that the foreign company itself may be exposed to currency risk if it conducts a lot of business in market with different currencies. Ideally the company has hedged against this, but if you invest in a foreign company through an ADR (or a GDR or another similar instrument), you may take on whatever risk the company hasn't hedged in addition to the currency risk that's present in the ADR/GDR conversion process. Here are a few articles that discuss currency risk specifically in the context of ADR's: (1), (2). Nestle, a Swiss company that is traded on US exchanges through an ADR, even addresses this issue in their FAQ for investors. There are other risks associated with instruments like ADR's and cross-listed companies, but normally arbitrageurs will remove these discontinuities quickly. Especially for cross-listed companies, this should keep the prices of highly liquid securities relatively synchronized." It's important to distinguish between speculation and investing. Buying something because you hope to make money on market fluctuations is speculation. Buying something and expecting to make money because your money is providing actual economic value is investing.  If Person A buys 100 shares of a stock with the intent of selling them in a few hours, and Person B buys 100 shares of the same stock with the intent of holding on to it for a year, then obviously at that point they both have the same risk. The difference comes over the course of the year. First, Person B is going to be making money from the economic value the company provides over the whole year, while the only way Person A can make money is from market fluctuation (the economic value the company provides over the course of an hour is unlikely to be significant). Person B is exposed to the risk of buying the stock, but that's counterbalanced by the profit from holding the stock for a year, while Person A just has the risk. Second, if Person A is buying a new stock every hour, then they're going to have thousands of transactions. So even though Person B assumed just as much risk as Person A for that one transaction, Person A has more total risk. "First, to mention one thing - better analysis calls for analyzing a range of outcomes, not just one; assigning a probability on each, and comparing the expected values. Then moderating the choice based on risk tolerance. But now, just look at the outcome or scenario of 3% and time frame of 2 days. Let's assume your investable capital is exactly $1000 (multiply everything by 5 for $5,000, etc.). A. Buy stock: the value goes to 103; your investment goes to $1030; net return is $30, minus let's say $20 commission (you should compare these between brokers; I use one that charges 9.99 plus a trivial government fee). B. Buy an call option at 100 for $0.40 per share, with an expiration 30 days away (December 23). This is a more complicated. To evaluate this, you need to estimate the movement of the value of a 100 call, $0 in and out of the money, 30 days remaining, to the value of a 100 call, $3 in the money, 28 days remaining. That movement will vary based on the volatility of the underlying stock, an advanced topic; but there are techniques to estimate that, which become simple to use after you get the hang of it. At any rate, let's say that the expected movement of the option price in this scenario is from $0.40 to $3.20. Since you bought 2500 share options for $1000, the gain would be 2500 times 2.8 = 7000. C. Buy an call option at 102 for $0.125 per share, with an expiration 30 days away (December 23). To evaluate this, you need to estimate the movement of the value of a 102 call, $2 out of the money, 30 days remaining, to the value of a 102 call, $1 in the money, 28 days remaining. That movement will vary based on the volatility of the underlying stock, an advanced topic; but there are techniques to estimate that, which become simple to use after you get the hang of it. At any rate, let's say that the expected movement of the option price in this scenario is from $0.125 to $ 1.50. Since you bought 8000 share options for $1000, the gain would be 8000 times 1.375 = 11000. D. Same thing but starting with a 98 call. E. Same thing but starting with a 101 call expiring 60 days out. F., ... Etc. - other option choices. Again, getting the numbers right for the above is an advanced topic, one reason why brokerages warn you that options are risky (if you do your math wrong, you can lose. Even doing that math right, with a bad outcome, loses). Anyway you need to ""score"" as many options as needed to find the optimal point. But back to the first paragraph, you should then run the whole analysis on a 2% gain. Or 5%. Or 5% in 4 days instead of 2 days. Do as many as are fruitful. Assess likelihoods. Then pull the trigger and buy it. Try these techniques in simulation before diving in! Please! One last point, you don't HAVE to understand how to evaluate projected option price movements if you have software that  does that for you. I'll punt on that process, except to mention it. Get the general idea? Edit P.S. I forgot to mention that brokers need love for handling Options too. Check those commission rates in your analysis as well." "JoeTaxpayer's answer adequately explained leverage and some of your risks.   Your risks also include: The firm's risk is that you will figure out a way to leave them with a negative account that contributes to another customer's profit and yet you disappear in a way that makes the negative account impossible to collect. Another risk is that you are not who you say you are, or that the money you invest is not yours.  These are called ""know your customer"" risks." Risks: The risk situation of the put option is the same whether you own the stock or not.  You risk $5 and stand to gain 0 to $250 in the period before expiration (say $50 if the stock reaches $200 and you sell).   Holding the stock or not changes nothing about that.  What is different is the consideration as to whether or not to buy a put when you own the stock.  Without an option, you are holding a $250 asset (the stock), and risking that money.  Should you sell and miss opportunity for say $300? Or hold and risk loss of say $50 of your $250?  So you have $250 at risk, but can lock in a sale price of $245 for say a month by buying a put, giving you opportunity for the $300 price in that month.  You're turning a risk of losing $250 (or maybe only $50 more realistically) into a risk of losing only $5 (versus the price your stock would get today). I don't know too much about the kelly criterion, but going by the other answers it sounds like it could be quite risky depending how you use it. I have been taught the first thing you do in trading is protect your existing capital and any profits you have made, and for this reason I prefer and use Position Sizing (PS). The concept with PS is that you only risk a small % of your capital on every trade, usually not more than 1%, however if you want to be very aggressive then not more than 2%. I use 1% of my capital for every trade. So if you are trading with an account of $40,000 and your risk R on every trade is 1%, then R = $400. As an example, say you decide to buy a stock at $10 and you work out your initial stop to be at $9.50, then our maximum risk R of $400 is divided by the stop distance of $0.50 to get your PS = $400/$0.50 = 800 shares. If the price then drops after your purchase, your maximum loss (subject to no slippage) would be $400.  If the price moves up you would raise your stop until your potential loss becomes smaller and smaller and then becomes a gain once your stop moves above your initial purchase price. The aim is to make your gains be larger than your losses. So if your average loss is kept to 1R or less then you should aim to get your average gains to 2R, 3R or more. This would be considered a good trading system where you will make regular profits even with a win ratio of 50%. "Diversification tends to protect you from big losses. But it also tends to ""protect"" you from big gains. In any industry, some companies provide good products and services and prosper while others have problems and fail. (Or maybe the winners are just lucky or they paid off the right politicians, whatever, not the point here.) If you put all your money in one stock and they do well, you could make a bundle. But if you pick a loser, you could lose your entire investment. If you buy a little stock in each of many companies, then some will go up and some will go down, and your returns will be an average of how everyone in the industry is doing. Suppose I offered to bet you a large sum of money that if I roll a die, it will come up 6. You might be reluctant to take that bet, because you can't predict what number will come up on one roll of a die. But suppose I offered to bet you a large sum of money that a die will come up 6, 100 times in a row. You might well take that bet, because the chance that it will turn up 6 time after time after time is very low. You reduce risk by spreading your bets. Anyone who's bought stock has surely had times when he said, ""Oh man! If only I'd bought X ten years ago I'd be a millionaire now!"" But quite a few have also said, ""If only I'd sold X ten years ago I wouldn't have lost all this money!""  I recently bought a stock a stock that within a few months rose to 10 times what I paid for it ... and then a few months later the company went bankrupt and the stock was worth nothing. I knew the company was on a roller coaster when I bought the stock, I was gambling that they'd pull through and I'd make money. I guessed wrong. Fortunately I gambled an amount that I was willing to lose." If you buy a stock and it goes up, you can sell it and make money. But if you buy a stock and it goes down, you can lose money. Unless you are buying millions of dollars worth of a stock at a time, your transaction is a drop in the bucket, unlikely to have any noticable effect on the stock price. As Ian says, it's more likely that you are just remembering the times when the price dropped after you bought. If you keep careful track, I suspect you will find that the price goes up more often than it goes down, or at least, that the stocks you buy go up as often as the average stock on the market goes up. If you actually kept records and found that's not true, the most likely explanation is bad luck. Or that someone has placed a voodoo curse on you. I suppose one could imagine other scenarios. Like, if you regularly buy stock based on recommendations by well-known market pundits, you could expect to see a temporary increase in price as thousands or millions of people who hear this recommendation rush to buy, and then a few days or weeks later people move on to the next recommendation, the market setttles down, and the price reverts to a more normal level. In that case, if you're on the tail end of the buying rush, you could end up paying a premium. I'm just speculating here, I haven't done a study to find if this actually happens, but it sounds plausible to me.