A metric unit of distance equal to 1021 meters or 1018 kilometers. One zettameter equals about 32.408 kiloparsecs (kpc) or 105 702 light years. This is a little more than the diameter of the Milky Way galaxy in which we live
Russ Rowlett (Director), How Many? A Dictionary of Units of Measurement, Center for Mathematics and Science Education University of North Carolina, USA 2005. http://www.unc.edu/~rowlett/units/dictA.html, (Unit of Meas and Covr Factors - Amer) {608}