Decaffeinated coffee
also: decaf
Coffee with most of its caffeine removed (typically 97% or more); reduced, not entirely caffeine-free.
Decaf is coffee that has had most of its caffeine stripped out while still green, before roasting. It is not caffeine-free: the common standard removes about 97% or more, so a typical cup still carries a small residual amount, usually a few milligrams. Heavy daily drinkers who switch to decaf in the afternoon should know it is low, not zero.
Decaffeination always happens on green coffee, and most methods rely on water to mobilize the caffeine, since caffeine is water-soluble. The methods differ in what actually pulls the caffeine out: a solvent (often ethyl acetate or methylene chloride), activated carbon plus water (the Swiss Water Process), or pressurized CO2. Each affects flavor differently, and modern decaf can taste very close to the original coffee.
The old reputation for flat, hollow decaf came from harsher early processing and stale beans, not from decaf being inherently bad. For a full comparison of how each method works, see decaf-processes.