# Inheritance Rules

This table describes the inheritance rules for various elements.

| Element       | extends                                                                         | implements          | Default Base Element |
| ------------- | ------------------------------------------------------------------------------- | ------------------- | -------------------- |
| **component** | one extensible component                                                        | multiple interfaces | `<aura:component>`   |
| **app**       | one extensible app                                                              | N/A                 | `<aura:application>` |
| **interface** | multiple interfaces using a comma-separated list (`extends="ns:intf1,ns:int2"`) | N/A                 | N/A                  |

**See Also**

- [Interfaces](/docs/platform/aura-platform/guide/oo-interfaces.md)