Question

How do we officially define a recession? A recovery? Who defines them? How many recessions have occurred in the USA since 1945?

Answer 1

Including 1945 there was 12 recessions have occurred in the USA .

A recession is a general downturn in any economy. A recession is associated with high unemployment, slowing gross domestic product, and high inflation.
Economic recession is a period of general economic decline and is typically accompanied by a drop in the stock market, an increase in unemployment, and a decline in the housing market. Generally, a recession is less severe than a depression. The blame for a recession generally falls on the federal leadership, often either the president himself, the head of the Federal Reserve, or the entire administration.

he technical indicator of a recession is two consecutive quarters of negative economic growth as measured by a country's gross domestic product (GDP), although the National Bureau of Economic Research (NBER) does not necessarily need to see this occur to call a recession.

Recovery reflect a large amount of monetary and fiscal stimulus, higher confidence and robust growth in emerging markets, low unemploment rate and lower inlation.