1. The voltage difference between any two specific points in a circuit.
2. The voltage developed across a component or conductor by the flow of current through the resistance or impedance of that component or conductor.
3. The decline in voltage in an electrical circuit because of the resistance in the conducting line.

This is why longer electrical runs in a building require thicker gauge wire and why AC power is transmitted over high-voltage lines.

Higher current requires thicker and more expensive wires, but higher voltage does not. The high-voltage lines are reduced by transformers near the end of the line.