The Zeroth Law

The zeroth law of thermodynamics states that if two thermodynamic systems are each in thermal equilibrium with a third, then they are in thermal equilibrium with each other.

A zero-day (also known as zero-hour or 0-day or day zero) vulnerability is an undisclosed computer-software vulnerability that hackers can exploit to adversely affect computer programs, data, additional computers or a network. It is known as a “zero-day” because it is not publicly reported or announced before becoming active, leaving the software’s author with zero days in which to create patches or advise workarounds to mitigate its actions.