A metric unit of mass representing 10^-18 grams, or 10^-21 kilograms, denoted by the symbol ag. It is used in mass spectrometry and nanotechnology to weigh individual large molecules, viruses or engineered nanoparticles. Measuring at this scale requires specialized nanomechanical resonators operating in a vacuum to detect the minute shift in frequency caused by the added mass.
Heard on the job
The mass spectrometer detected a peptide fragment weighing roughly fifty attograms.