A relay is basically a controllable switch that connects a supply voltage to a load. If the relay is switch such that the load is not connected, that could be considered an open load. If it is...
Yep.
"Point defects are defects which are not extended in space in any dimension. There is not strict limit for how small a "point" defect should be, but typically the term is used to mean defects...
Defects in crystals are known as thermodynamics defects because crystal defects are as a result of thermodynamics equilibrium and also increase in entropy has also contributed to it.