# What is the difference between these notations and terms?

I can't tell if they're being used interchangeably or if there's some nuanced difference betweem them. Here they are:

$$E^∘$$

$$E_0$$

$$E_h$$

$$E^⦵$$

If I understand correctly, electrode potential is the same as reduction potential. Redox potential can be both reduction potential and oxidation potential.

EDIT 1:

The context is electrochemistry. andselisk in the comments asked if it was $$E^⦵$$ or $$E^∘$$. When I had the superscripted $$0$$, I actually meant $$∘$$, as andselisk wrote. I hadn't seen that the sites had used this, and not a zero. andselisk also included this other symbol (⦵) I hadn't seen until now, but I'm now wondering about it too, as I've seen it is used in some equations relating to the topic of electrode/reduction potentials.

EDIT 2:

Here are some links that show why I'm confused:

This Wikipedia article #1 notates reduction potential as $$E_0$$, whereas this Wikipedia article #2 notates standard electrode potential as $$E^∘$$. Now, as said, I believe that

reduction potential = electrode potential

Perhaps the first article is referring to the unknown absolute reduction/electrode potential, and the second article is referring to standard reduction/electrode potential.

EDIT 3:

Perhaps there actually is a difference between reduction potential and electrode potential. Maybe they both describe the exact same phenomenon, but in different contexts. Here's the nuance I propose:

A species can only be said to have an electrode potential when this species exists as an electrode. Its electrode potential is the same as its reduction potential, but it is being viewed in the context of an electrode. One could still refer to the electrode potential as a reduction potential.

However, if one's is talking about the reduction potential of a species when it isn't an electrode, it is simply a reduction potential.

If it is an electrode: can use both reduction potential and electrode potential.

If it isn't an electrode: can only use reduction potential.