A bond is defined as an interest-bear- ing certificate issued by a govern ment or business, promising to pay the holder a specified sum on a specified date. Common wisdom says bonds are a safe haven from stock market turmoil. Does that mean you should buy bonds if that turmoil comes from recession or inflation? Complicating the situation is the fact that there is no one-size-fits-all-situations bond.

The Treasury Department issues bonds, so do corporations, municipalities and banks. There are short-term bonds and long-term bonds; bonds with pristine credit ratings and junk bonds. Remember, while bonds may protect you in hard economic times from the deep dives that stocks sometimes take, there is no guarantee you won't lose money.

With bonds, you can get hurt while standing on the sidelines. Stability versus volatilityIt's a given that most people, especially as they near retirement and need to reduce volatility in their portfolio, should have a smattering of bonds for stability and to provide fixed-income. The ratio of bonds to equities and cash depends on your needs and your risk tolerance.

We won't specifically address allocation in this article, but we will try to provide some guidance for when it's appropriate to load up a bit more on your bond allocation. Cash, U.S. bonds and foreign bondsDavid Marotta, president of Marotta Asset Management in Charlottesville, Va., includes three asset classes in the stability portion of his clients' portfolios. The first is "short money," comprised mainly of money markets and, occasionally, short-term CDs; assets that mature in less than two years. Second is US bonds, and the third is foreign bonds.

"Short money has probably been the riskiest investment over the past couple of years," says Marotta. "The dollar has dropped in value and its buying power has dropped tremendously. By proxy, the second riskiest investment is US bonds. They've appreciated some in the recent market downturn, they've paid a little bit better interest rate, but in terms of purchasing power, they've been one of the worst investments in the last two years.

"Foreign bonds do the best during a recession and during inflation. During a recession, the bond category as a whole will do well, but during inflationary times, the US dollar is dropping in value. Your foreign bonds are going to get both the good return you get in a bond portfolio during a recession and an extra kick because the value of the US dollar is dropping. "When the dollar drops, your foreign bonds are going up in value because they're invested in foreign currencies, which aren't being devalued as much as the dollar. When you invest in foreign bonds in this mode, you want to invest in unhedged foreign bonds."

Hedged versus unhedgedSince individual bonds can be too pricey for many individual investors, consider bond funds. An unhedged foreign bond fund is one that is denominated in foreign currencies. Sometimes the word hedged or unhedged will be in the funds title, such as PIMCO Foreign Bond (Unhedged).

If it's not noted in the fund name, check the fund's description or profile. You're deliberately exposing yourself to currency fluctuations when you buy an unhedged bond or bond fund. A foreign bond fund that is U.S. dollar hedged will limit its exposure to foreign currencies. In other words, you're limiting your exposure to currency fluctuations.

Treasury BondsJames Shelton, chief investment officer at Kanaly Trust Co. in Houston, says this isn't a good time to buy Treasuries, and think twice before buying corporate bonds. Keep in mind that when bonds become popular, the price you pay for a bond rises and the yield drops.