, seems to reflect a mistaken belief that the word was originally and is still properly only an adjective.
As the entries here show, however, the noun is in fact the older form, dating to the 16th century.
Relative pronouns are pronouns that are used to introduce a clause that provides more information about a noun.
At this point, you don't need to learn the rules of their usage, but you should recognize them when you see or hear them.
In economics, a depression is a sustained, long-term downturn in economic activity in one or more economies.
It is a more severe downturn than an economic recession, which is a slowdown in economic activity over the course of a normal business cycle.
A depression is an unusual and extreme form of recession.
Depressions are characterized by their length, by abnormally large increases in unemployment, falls in the availability of credit (often due to some form of banking or financial crisis), shrinking output as buyers dry up and suppliers cut back on production and investment, large number of bankruptcies including sovereign debt defaults, significantly reduced amounts of trade and commerce (especially international trade), as well as highly volatile relative currency value fluctuations (often due to currency devaluations).