"Femtometer" Natural Recordings by Native Speakers
A femtometer (fm) is a unit of length in the metric system, equal to 10^-15 meters. It is a billionth of a nanometer or one quadrillionth of a meter.
A femtosecond is a unit of time that is equal to one quadrillionth (10^(-15)) of a second. It is a very short period of time, and is often used to measure extremely fast events or phenomena in fields such as physics, chemistry, and biology.