Which prefix denotes 10^-12?

The prefix that denotes 10^-12 is "pico." This term is derived from the Spanish word "pico," which means "small." In the metric system, pico is used to represent a factor of one trillionth, or 0.000000000001, of a unit.

Using prefixes in scientific measurement allows for easier expression of extremely large or small quantities. For example, a picometer is one trillionth of a meter, and this makes it practical to measure very small dimensions, such as atomic scales in physics or chemistry.

The other prefixes listed represent different orders of magnitude: femto denotes 10^-15, atto represents 10^-18, and yocto signifies 10^-24. Thus, while they all relate to small quantities, pico is specifically the prefix that corresponds to 10^-12.