''Micri-'' (

unit symbol A unit of measurement is a definite magnitude of a quantity, defined and adopted by convention or by law, that is used as a standard for measurement of the same kind of quantity. Any other quantity of that kind can be expressed as a multi ...

''mc-'') is an archaic non- SI

decimal The decimal numeral system (also called the base-ten positional numeral system and denary or decanary) is the standard system for denoting integer and non-integer numbers. It is the extension to non-integer numbers of the Hindu–Arabic numeral ...

metric prefix A metric prefix is a unit prefix that precedes a basic unit of measure to indicate a multiple or submultiple of the unit. All metric prefixes used today are decadic. Each prefix has a unique symbol that is prepended to any unit symbol. The pre ...

for 10⁻¹⁴. It was proposed as a prefix for the CGS-unit of energy, the

erg The erg is a unit of energy equal to 10−7joules (100 nJ). It originated in the Centimetre–gram–second system of units (CGS). It has the symbol ''erg''. The erg is not an SI unit. Its name is derived from (), a Greek word meaning 'work' o ...

. The ''

micrierg The erg is a unit of energy equal to 10−7joules (100 nJ). It originated in the Centimetre–gram–second system of units (CGS). It has the symbol ''erg''. The erg is not an SI unit. Its name is derived from (), a Greek word meaning 'work' o ...

'' was proposed in 1922 by

William Draper Harkins William Draper Harkins (December 28, 1873 – March 7, 1951) was an American physical chemist, noted for his contributions to surface chemistry and nuclear chemistry. Harkins researched the structure of the atomic nucleus and was the first to p ...

as a unit of energy equating to 10⁻¹⁴ erg, the equivalent to 10⁻²¹

joule The joule ( , ; symbol: J) is the unit of energy in the International System of Units (SI). It is equal to the amount of work done when a force of 1 newton displaces a mass through a distance of 1 metre in the direction of the force applied ...

, as a convenient unit to measure the

surface energy In surface science, surface free energy (also interfacial free energy or surface energy) quantifies the disruption of intermolecular bonds that occurs when a surface is created. In solid-state physics, surfaces must be intrinsically less energe ...

molecule A molecule is a group of two or more atoms held together by attractive forces known as chemical bonds; depending on context, the term may or may not include ions which satisfy this criterion. In quantum physics, organic chemistry, and bioch ...

s in

surface chemistry Surface science is the study of physical and chemical phenomena that occur at the interface of two phases, including solid–liquid interfaces, solid–gas interfaces, solid–vacuum interfaces, and liquid–gas interfaces. It includes the fiel ...

. It saw limited use. One

electronvolt In physics, an electronvolt (symbol eV, also written electron-volt and electron volt) is the measure of an amount of kinetic energy In physics, the kinetic energy of an object is the energy that it possesses due to its motion. It is defi ...

is about 160 micriergs. In 1991, the micrierg was officially designated the '' zeptojoule'' when the ''

zepto A metric prefix is a unit prefix that precedes a basic unit of measure to indicate a multiple or submultiple of the unit. All metric prefixes used today are decadic. Each prefix has a unique symbol that is prepended to any unit symbol. The pre ...

''- prefix for 10⁻²¹ was officially adopted.

References

Greek words and phrases Metric prefixes Decimal prefixes {{vocab-stub