---
id: fast-foundation.foundationelementdefinition.baseclass
title: FoundationElementDefinition.baseClass property
hide_title: true
---
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[@microsoft/fast-foundation](./fast-foundation.md) &gt; [FoundationElementDefinition](./fast-foundation.foundationelementdefinition.md) &gt; [baseClass](./fast-foundation.foundationelementdefinition.baseclass.md)

## FoundationElementDefinition.baseClass property

The actual FAST base class of the component if different from the class used to compose.

<b>Signature:</b>

```typescript
baseClass?: Constructable;
```