Quantitative Easing (QE)
Large-scale asset purchases by central banks to inject liquidity and lower long-term rates.
In depth
Used when policy rates near zero (zero lower bound). Fed, ECB, BoE, BoJ have all used QE. Inflates central bank balance sheets and asset prices. "Quantitative tightening" (QT) is the reverse — letting balance sheet shrink as bonds mature.