Washington » There's a reason it's called the Great Depression. The epic hard times of the 1930s became the best-known depression in American history, but it doesn't necessarily take that kind of nightmarish suffering to trigger the D-word today.

In fact, some economists worry that the economy could be sinking into a milder depression, the kind spelled with a lowercase "d."

This isn't the 1930s of bread lines, rampant unemployment, a wipeout in the stock market. But, unlike recessions, which are easy to define, there are no firm rules for what makes a depression. Everyone at least seems to agree there hasn't been one since the dark days of Hoover and FDR.

That said, with each new hard-times headline, most recently an alarming economic contraction of 6.2 percent in the fourth quarter, it seems that something more drastic than a recession could be on its way.

"It's not going to be acknowledged until years go by. Because you have to see it behind you," said Peter Morici, a business professor at the University of Maryland.

No one disputes that today's economic downturn qualifies as a recession. Recessions have two handy definitions, both in effect now -- two straight quarters of economic contraction, or when the National Bureau of Economic Research makes the call.

Declaring a depression is much trickier. By one definition, it's a downturn of three years or more with a 10 percent drop in economic output and unemployment above 10 percent. The current recession doesn't qualify -- 15 months old and 7.6 percent unemployment.

Another definition says a depression is a sustained recession during which the populace has to dispose of tangible assets to pay for everyday living. For some families, that's happening now.

Morici defines a depression is a recession that "does not self-correct" because of fundamental structural problems in the economy, such as broken banks or a huge trade deficit.

The Great Depression retains the heavyweight crown. Unemployment peaked at more than 25 percent. From 1929 to 1933, the economy shrank 27 percent. The stock market lost 90 percent of its value from boom to bust.

And although the 2008 stock market was the worst since 1931, the Dow Jones industrials would have to fall about 5,000 more points to approach what happened in the Great Depression.

Few economists expect this downturn will be the sequel, but nobody can say when or whether the downturn may deepen from a recession. In his prime-time address to Congress last week, President Barack Obama acknowledged "difficult and trying times" but sought to rally the nation with an upbeat vow that "we will rebuild, we will recover."

Despite the tempered optimism, consumer confidence has fallen off the table, stocks are at 12-year lows, layoffs come by the tens of thousands and credit remains tight.

Policymakers and economists note there are safeguards in place that weren't there in the 1930s -- deposit insurance, unemployment insurance and an ability by the government to hurl trillions of dollars at the problem, even if it means printing money.

Most postwar U.S. recessions have come after the Fed has increased interest rates to cool rapid growth and inflation. Later, the Fed lowers rates and helps restart the economy, with the housing and auto sectors leading the way. This time, as Senate Banking Committee Chairman Chris Dodd, D-Conn., said, "Our housing and auto sectors are leading us into it."

What's more, the central bank has already lowered the short-term rates it controls to zero, eliminating that leverage, and there are no guarantees the massive economic stimulus package and series of bank bailouts will stave off a nightmare recession, or worse.