# Inline Syntax
source: https://docs.chalk.ai/docs/notebook-inline

## Defining features inline in notebooks

In notebooks, you can define features inline using the syntax shown below.

Consider the following feature class definition for RocketEngine

```
from chalk.features import features

@features
class RocketEngine:
    id: int
    mass: float
    volume: float
    thrust: float
```

If we wanted to define a feature inline in a notebook cell, we could do so using the underscore syntax below:

```
RocketEngine.density: float = _.mass / _.volume
```