Pico-
Pico- (symbol p) is a unit prefix in the metric system denoting one trillionth, a factor of 10−12 (0.000000000001).
Derived from the Spanish pico, meaning peak, beak, bit, this was one of the original 12 prefixes defined in 1960 when the International System of Units was established.
The radius of atoms range from 25 picometers (hydrogen) to 260 picometers (caesium). One picolight-year is about nine kilometers (six miles).
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