飞(femto)是国际单位制的词头，表示10的-15次方。词源为丹麦语词汇 femten，表示「fifteen（即，十五）」。符号 f。

例： 1 fF = 10 F

Femto- (symbol f) is a unit prefix in the metric system denoting a factor of 10 or 0.000000000000001. Adopted by the 11th General Conference on Weights and Measures, it was added in 1964 to the SI. It is derived from the Danish word femten, meaning "fifteen".