The word Jiffy is an informal term for any unspecified short period of time, as in “I’ll be back in a jiffy”. From this it has acquired a number of more precise applications for short, very short, or extremely short periods of time. Known since the 18th century, the word’s origin is unclear, though one suggestion is that it was thieves’ secret word for lightning.
The earliest technical usage for jiffy was defined by Gilbert Newton Lewis (1875–1946). He proposed a unit of time called the “jiffy” which was equal to the time it takes light to travel one centimetre. It has since been redefined for different measurements depending on the field of study including:
* In electronics, a jiffy is the time between alternating current power cycles, 1/60 or 1/50 of a second in most countries.
* In computing, a jiffy is the duration of one tick of the system timer interrupt.
* In physics (particularly in quantum physics) and often in chemistry, a jiffy is defined as the time taken for light to travel some specified distance. In astrophysics and quantum physics a jiffy is, the time it takes for light to travel one fermi, which is the size of a nucleon. One fermi is 10−15 m, so a jiffy is about 3 × 10−24 seconds.