I sometimes see in some places that power is defined as ½ V² / R.
Where does the ½ come from?
Well, But it's true, there is no such thing as RMS power.What do you mean there is no such thing as RMS power? Why would you make such a blatantly incorrect statement?
Term "RMS" refers only to effective value of a AC voltage and current.
And we should not use the term "RMS" to description the real (true) power.
The true power is simple average value of the instantaneous power.
And for this we don't need roots and the square.
So RMS power is inaccurate term, that have no logical justification.