Smart answer:

Your search for What is superconductivity returned the following results:

a phenomenon of exactly zero electrical resistance and expulsion of magnetic fields occurring in certain materials when cooled below a characteristic critical temperature

Superconductivity is a phenomenon of exactly zero electrical resistance and expulsion of magnetic fields occurring in certain materials when cooled below a characteristic critical temperature.

Source:

a phenomenon of exactly zero electrical resistance and expulsion of magnetic flux fields occurring in certain materials, called superconductors, when cooled below a characteristic critical temperature

Superconductivity is a phenomenon of exactly zero electrical resistance and expulsion of magnetic flux fields occurring in certain materials, called superconductors, when cooled below a characteristic critical temperature.

Source:

the weird phenomenon of zero electrical resistance that occurs when some materials are cooled below a critical temperature

Superconductivity is the weird phenomenon of zero electrical resistance that occurs when some materials are cooled below a critical temperature.

a phenomenon of exactly zero electrical resistance and expulsion of magnetic flux fields occurring in certain materials when cooled below a characteristic critical temperature

Explanation: Superconductivity is a phenomenon of exactly zero electrical resistance and expulsion of magnetic flux fields occurring in certain materials when cooled below a characteristic critical temperature.

a rare physical state in which matter is able to conduct electricity without any resistance

Superconductivity is a rare physical state in which matter is able to conduct electricity without any resistance.

Source:

a phenomenon occurring in certain materials at extremely low temperatures (on the order of −200 degrees Celsius)

Superconductivity, discovered in 1911 by Heike Kamerlingh Onnes, is a phenomenon occurring in certain materials at extremely low temperatures (on the order of −200 degrees Celsius), characterized by exactly zero electrical resistance and exclusion of the interior magnetic field (the Meissner effect).

Source:

a phenomenon in which electricity flows without resistance from the material the material moves through, so that no energy is lost in the process

Superconductivity is a phenomenon in which electricity flows without resistance from the material the material moves through, so that no energy is lost in the process.

the astonishing physical phenomenon of a material conducting electrical current without any resistance, i.e. without any ohmic losses

Superconductivity is the astonishing physical phenomenon of a material conducting electrical current without any resistance, i.e. without any ohmic losses.

a quantum mechanical phenomenon in macroscopic scale

Like ferromagnetism and atomic spectral lines, superconductivity is a quantum mechanical phenomenon in macroscopic scale.

a quantum-mechanical phenomenon, superconductor-insulator-superconductor layers

Since superconductivity is a quantum-mechanical phenomenon, superconductor-insulator-superconductor layers can 'leak' through the insulator (if superconductor-insulator-superconductor layers is thin enough) into the other superconductor.

Source: