Based on your financial expertise, provide your response or viewpoint on the given financial question or topic. The response format is open.

How to evaluate investment risk in practical terms
Generally investing in index-tracking funds in the long term poses relatively low risk (compared to "short term investment", aka speculation). No-one says differently. However, it is a higher risk than money-market/savings/bonds. The reason for that is that the return is not guaranteed and loss is not limited. Here volatility plays part, as well as general market conditions (although the volatility risk also affects bonds at some level as well). While long term trend may be upwards, short term trend may be significantly different. Take as an example year 2008 for S&P500. If, by any chance, you needed to liquidate your investment in November 2008 after investing in November 1998 - you might have ended up with 0 gain (or even loss). Had you waited just another year (or liquidated a year earlier) - the result would be significantly different. That's the volatility risk. You don't invest indefinitely, even when you invest long term. At some point you'll have to liquidate your investment. Higher volatility means that there's a higher chance of downward spike just at that point of time killing your gains, even if the general trend over the period around that point of time was upward (as it was for S&P500, for example, for the period 1998-2014, with the significant downward spikes in 2003 and 2008). If you invest in major indexes, these kinds of risks are hard to avoid (as they're all tied together). So you need to diversify between different kinds of investments (bonds vs stocks, as the books "parrot"), and/or different markets (not only US, but also foreign).