The ohm (symbol: Ω) is the SI (International System of Units) unit of **electrical resistance**.
1 ohm is defined as the resistance that allows 1 ampere of current to flow when a potential difference of 1 volt is applied across it. In other words, if you apply 1 volt of electrical potential across a resistor of 1 ohm, it will allow a current of 1 ampere to flow.
Mathematically, it can be expressed using Ohm's Law:
\[ R = \frac{V}{I} \]
where:
- \( R \) is the resistance in ohms (Ω),
- \( V \) is the voltage in volts (V),
- \( I \) is the current in amperes (A).