# candela, cd (unit)
This page documents an [OPTIMADE](https://www.optimade.org/) [Unit Definition](https://schemas.optimade.org/#definitions). See [https://schemas.optimade.org/](https://schemas.optimade.org/) for more information.
**ID: [`https://schemas.optimade.org/defs/v1.2/units/si/1967/base/candela`](https://schemas.optimade.org/defs/v1.2/units/si/1967/base/candela.md)**
**Definition name:** `candela`
**Unit name:** candela
**Latin symbol:** cd
**Display symbol:** cd
**Description:** The candela is the SI base unit of luminous intensity in a given direction defined in from the radiation of a black body at the temperature of freezing platinum as defined at the 9th CGPM meeting in 1948, clarified at the 13th CGPM Meeting in 1967, resolution 5; and implicitly redefined due to the 1967 SI redefinition of the second.
At the 13th CGPM Meeting in 1967, resolution 5 the previous definition from the 9th CGPM meeting in 1948 was rephrased to be more clear: "The candela is the luminous intensity, in the perpendicular direction, of a surface of 1/600000 square metre of a black body at the temperature of freezing platinum under a pressure of 101325 newtons per square metre."
Furthermore, the SI 1967 definition of the candela references:
- the SI 1960 metre (https://schemas.optimade.org/defs/v1.2/units/si/1960/base/metre).
- the SI 1967 derived newton unit (https://schemas.optimade.org/defs/v1.2/units/si/1967/named/newton) equal to kilogram·metre·second⁻², referencing the SI 1960 kilogram (https://schemas.optimade.org/defs/v1.2/units/si/1960/base/kilogram) and metre (https://schemas.optimade.org/defs/v1.2/units/si/1960/base/metre); and the 1967 definition of the second (https://schemas.optimade.org/defs/v1.2/units/si/1967/base/second).
**Resources:**
- [Definition at the 13th CGPM meeting (1967)](https://www.bipm.org/en/committees/cg/cgpm/13-1967/resolution-5)
- [Previous definition at the 9th CGPM meeting (1948)](https://www.bipm.org/en/committees/cg/cgpm/9-1948)
- [Wikipedia article describing the unit](https://en.wikipedia.org/wiki/Candela)
**Formats:** [[JSON](candela.json)] [[MD](candela.md)]
**JSON definition:**
``` json
{
"$id": "https://schemas.optimade.org/defs/v1.2/units/si/1967/base/candela",
"$schema": "https://schemas.optimade.org/meta/v1.2/optimade/physical_unit_definition.json",
"title": "candela",
"symbol": "cd",
"display-symbol": "cd",
"description": "The candela is the SI base unit of luminous intensity in a given direction defined in from the radiation of a black body at the temperature of freezing platinum as defined at the 9th CGPM meeting in 1948, clarified at the 13th CGPM Meeting in 1967, resolution 5; and implicitly redefined due to the 1967 SI redefinition of the second.\n\nAt the 13th CGPM Meeting in 1967, resolution 5 the previous definition from the 9th CGPM meeting in 1948 was rephrased to be more clear: \"The candela is the luminous intensity, in the perpendicular direction, of a surface of 1/600000 square metre of a black body at the temperature of freezing platinum under a pressure of 101325 newtons per square metre.\"\n\nFurthermore, the SI 1967 definition of the candela references:\n\n- the SI 1960 metre (https://schemas.optimade.org/defs/v1.2/units/si/1960/base/metre).\n- the SI 1967 derived newton unit (https://schemas.optimade.org/defs/v1.2/units/si/1967/named/newton) equal to kilogram\u00b7metre\u00b7second\u207b\u00b2, referencing the SI 1960 kilogram (https://schemas.optimade.org/defs/v1.2/units/si/1960/base/kilogram) and metre (https://schemas.optimade.org/defs/v1.2/units/si/1960/base/metre); and the 1967 definition of the second (https://schemas.optimade.org/defs/v1.2/units/si/1967/base/second).",
"resources": [
{
"relation": "Definition at the 13th CGPM meeting (1967)",
"resource-id": "https://www.bipm.org/en/committees/cg/cgpm/13-1967/resolution-5"
},
{
"relation": "Previous definition at the 9th CGPM meeting (1948)",
"resource-id": "https://www.bipm.org/en/committees/cg/cgpm/9-1948"
},
{
"relation": "Wikipedia article describing the unit",
"resource-id": "https://en.wikipedia.org/wiki/Candela"
}
],
"standard": {
"name": "si",
"year": 1967,
"category": "base",
"symbol": "cd"
},
"x-optimade-definition": {
"label": "candela_si_1967_base",
"kind": "unit",
"format": "1.2",
"version": "1.2.0",
"name": "candela"
}
}
```