```Python
say_hi(name=None)  # This works, None is valid 🎉
```

The good news is, once you are on Python 3.10 you won't have to worry about that, as you will be able to simply use `|` to define unions of types:

{* ../../docs_src/python_types/tutorial009c_py310.py hl[1,4] *}

And then you won't have to worry about names like `Optional` and `Union`. 😎

#### Generic types { #generic-types }

/// note

When defining a <a href="https://docs.pydantic.dev/latest/concepts/types/#unions" class="external-link" target="_blank">`Union`</a>, include the most specific type first, followed by the less specific type. In the example below, the more specific `PlaneItem` comes before `CarItem` in `Union[PlaneItem, CarItem]`.

/// note | Hinweis

Wenn Sie eine <a href="https://docs.pydantic.dev/latest/concepts/types/#unions" class="external-link" target="_blank">`Union`</a> definieren, listen Sie den spezifischeren Typ zuerst auf, gefolgt vom weniger spezifischen Typ. Im Beispiel unten steht `PlaneItem` vor `CarItem` in `Union[PlaneItem, CarItem]`.

///

/// note | Nota

* 👥 Update FastAPI People - Contributors and Translators. PR [#13845](https://github.com/fastapi/fastapi/pull/13845) by [@tiangolo](https://github.com/tiangolo).

## 0.115.14

### Fixes

* 🐛 Fix support for unions when using `Form`. PR [#13827](https://github.com/fastapi/fastapi/pull/13827) by [@patrick91](https://github.com/patrick91).

### Docs