Define capacitor reactance. Write its SI units.

Explanation

### Step-by-Step Solution

1. **Definition of Capacitive Reactance**:
- Capacitive reactance is defined as the opposition that a capacitor offers to the flow of alternating current (AC) in an electrical circuit. This opposition is not due to resistance but is a result of the capacitor's ability to store and release energy in the form of an electric field.

2. **Mathematical Expression**:
- The capacitive reactance (denoted as \(X_c\)) can be mathematically expressed as:
\[
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