The quality of being paradoxical.

plural of paradoxicality

The perceived failure of European countries to translate scientific advances into marketable innovations.

(relativity) The phenomenon in which two observers who start together with identical clocks, follow different timelines, and then rejoin can have different elapsed times on their clocks, especially if one travels at a relativistic speed.

(relativity) The clock paradox.

(astronomy) The observation that the night sky is mostly dark, yet, in a boundless universe of stars, every line of sight from the eye must eventually intercept the surface of a star.

(economics) The apparent paradox that a rent seeker wanting political favours can bribe politicians at a cost much lower than the value of the favour to the rent seeker.

plural of Klein paradox

(quantum mechanics) A surprising result of applying the Dirac equation to the problem of electron scattering from a potential barrier. In non-relativistic quantum mechanics, electron tunnelling into a barrier is observed, with exponential damping. However, if the potential is of the order of the electron mass, V∼mc², the barrier is nearly transparent; moreover, as the potential approaches infinity, the reflection diminishes and the electron is always transmitted.

The linguistic paradox that, if there are unnameable things, their existence cannot be indicated without naming them in some way.