The
benefit, often
hidden, that can be gained from an
event that was seen as unfavorable. The old saying is
"In every cloud, there is a silver lining."
A political example in the United States would be that many Democrats predict that their winning of many congressional seats in the 2002 election due to voter backlash will be the silver lining in what they consider
to be the dark cloud of Republican opponent George W. Bush's election to the Presidency in 2000.
Many organizations have named themselves after this expression. For example, there is a bipolar disorder support group at www.a-silver-lining.org.
Other silver linings are even less obvious, such as the possible anti-cancer benefits of CLA, a substance found in milk fat (i.e. ice cream, butter, and other fattening substances.)
(For those who are interested, the bit on CLA is 1996 reseach done by the American Council on Science and Health, or ACSH)