---
id: fast-element.fastelementdefinition.define
title: FASTElementDefinition.define() method
hide_title: true
---
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[@microsoft/fast-element](./fast-element.md) &gt; [FASTElementDefinition](./fast-element.fastelementdefinition.md) &gt; [define](./fast-element.fastelementdefinition.define.md)

## FASTElementDefinition.define() method

Defines a custom element based on this definition.

<b>Signature:</b>

```typescript
define(registry?: CustomElementRegistry): this;
```

## Parameters

|  Parameter | Type | Description |
|  --- | --- | --- |
|  registry | CustomElementRegistry | The element registry to define the element in. |

<b>Returns:</b>

this
