noun
- Plural of femtometer; units of length equal to one quadrillionth of a meter (10⁻¹⁵ m), used in nuclear and particle physics.
Usage: technical; scientific; often abbreviated as fm
Examples
- The nucleus of an atom has a diameter measured in femtometers.
- Physicists use femtometers to describe the size of subatomic particles.
- The radius of a proton is approximately 0.84 femtometers.
- Experiments at the particle accelerator measured distances in femtometers.
- Nuclear forces operate at scales of a few femtometers.