This quantity characteristically scales logarithmically with evolution time in systems displaying many-body localization. This quantity evolves over time to form an inverted V shape on the Page curve. For a tripartite quantum system, this quantity obeys strong subadditivity. For pure states, the distillable and squashed (10[1])entanglements reduce to this quantity. For a system with density matrix rho, this quantity equals the negative trace of rho times log rho. (10[1])By the Bekenstein–Hawking formula, the area of a black hole is proportional (10[1])to its value of this quantity. In classical information theory, this quantity expresses the absence of information about a system and is measured in shannons. For 10 points, name this quantity that increases in accordance with the second law of thermodynamics. ■END■