# Candela (Cd)

**Candela** is the unit of luminous intensity, a measure of the amount of light emitted in a particular direction. It's one of the seven base units in the International System of Units (SI).

## What Does Candela Mean?

- **Luminous intensity:** This refers to the power of light emitted in a specific direction. It’s different from luminous flux, which measures the total amount of light emitted in all directions.
- **Directionality:** Candela is a measure of light intensity in a specific direction, unlike luminous flux, which is a measure of total light output.

## Is Candela Used in Light Therapy?

When measuring the intensity of light used in [light therapy](/content/what-is-light-therapy-and-is-it-right-for-you/index.html) devices, such as light boxes or [light therapy glasses](/content/what-are-light-therapy-glasses-2/index.html), candela is often used. This unit is crucial for ensuring that the device is providing the correct amount of light to effectively treat conditions like [seasonal affective disorder (SAD)](/content/what-is-seasonal-affective-disorder-sad/index.html).