# in

### Description

`in` is used to check if a value is present in a list or a [taxonomy](https://docs.atfinity.io/guides/glossary/taxonomy). If it is, the expression evaluates true. On the left side of `in`, there is always a single value. The list of options, which could be a taxonomy, goes on the right side of `in`.

### Example

If a [document](https://docs.atfinity.io/guides/glossary/document) is only relevant to parties who reside in the European Union, attach this condition to it:

```
p is Person
p.domicile in EUCountries
```

There is one answer for what the domicile of a person or an entity is, so this is a single value. With the expression in the example, you check whether this value is part of the taxonomy `EUCountries`, which predictably consists of a list of all the member states of the European Union.

If `p.domicile` is the United Kingdom, the condition evaluates to false. The document will not be included in the [case](https://docs.atfinity.io/guides/glossary/case). If `p.domicile` is Belgium, the condition evaluates to true, meaning the document is included.