# unit/defunit-1.0.0¶

Define a new physical unit.

#### Description

Defines a new unit. It can be used to either:

• Define a new base unit.
• Create a new unit name that is a equivalent to a given unit.

The new unit must be defined before any unit tags that use it.

### Schema Definitions ¶

This type is an object with the following properties:
• name
 string Required
The name of the new unit.

No length restriction
Must match the following pattern:
[A-Za-z_][A-Za-z0-9_]+

• unit
 object
The unit that the new name is equivalent to. It is optional, and if not provided, or null, this defunit defines a new base unit.

This node must validate against any of the following:

### Original Schema ¶

%YAML 1.1
---
$schema: "http://stsci.edu/schemas/yaml-schema/draft-01" id: "http://stsci.edu/schemas/asdf/unit/defunit-1.0.0" title: Define a new physical unit. description: | Defines a new unit. It can be used to either: - Define a new base unit. - Create a new unit name that is a equivalent to a given unit. The new unit must be defined before any unit tags that use it. tag: "tag:stsci.edu:asdf/unit/defunit-1.0.0" type: object properties: name: description: The name of the new unit. type: string pattern: "[A-Za-z_][A-Za-z0-9_]+" unit: description: | The unit that the new name is equivalent to. It is optional, and if not provided, or null, this defunit defines a new base unit. anyOf: -$ref: "unit-1.0.0"
- type: "null"

required: [name]
...