Question

What does femto mean?

Answer 1

Femto:

1. Femto (symbol f) is a metric unit prefix that denotes a factor of ${10}^{-15}$.
2. In 1964, it was added to the International System of Units (SI). It is derived from the Danish word femten, which means “fifteen”.
3. It has a spelling that is vaguely similar to fermi, which was introduced earlier to mean a femtometer.