Standard electrode potential.

Explanation

### Step-by-Step Solution:

1. **Definition of Standard Electrode Potential**:
- The standard electrode potential (E°) is defined as the measure of the tendency of a metallic electrode to either lose electrons (oxidation) or gain electrons (reduction) when it is in contact with a solution of its own salt.

2. **Conditions for Measurement**:
- The measurement of standard electrode potential is taken under specific conditions:
- The solution must be of one molar concentration (1 M).
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