> For the complete documentation index, see [llms.txt](https://docs.chatlayer.ai/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.chatlayer.ai/nlp/natural-language-processing-nlp/detect-information-with-entities/system-entities.md).
# System entities
System entities are Chatlayer's built-in predefined entities that match a certain general pattern that is widely used.
You can think of system entities as [match entities ](/nlp/natural-language-processing-nlp/detect-information-with-entities/match-entities.md)that are pre-made just because they fit regular, typical patterns that would be widely used inside bot conversations.
System entities tab.
Chatlayer.ai supports the following system entities:
| Variable name | | Example input by user | Example result in session |
| --------------------- | --------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | -------------------------------------------------------- | --------------------------------------------------------------------------------------------------------------- |
| `sys.email` | Validates if the user input has an email format | "" | `sys: {email: 'ilovebots@chatlayer.ai'}` |
| `sys.phone_number` | Accepts numbers with more than 6 and fewer than 17 numbers in them | "+32 487 23 02 03" | `sys: {phone_number: '(+32) 487230203'}` |
| `sys.ordinal` | | "5th" | `sys: {ordinal: '5'}` |
| `sys.amount_of_money` | | "5 euro" | `sys: {amount_of money: '5', amount_of_money_currency: 'EUR'}` |
| `sys.distance` | | "5 kilometers" | `sys: {distance: '5', distance_unit: 'kilometre'}` |
| `sys.number` | Recognizes any number. | "eighty eight" | `sys: {number: '88'}` |
| `sys.quantity` | | "3 liters" | `sys: {quantity: '3', quantity_unit: 'litre'}` |
| `sys.temperature` | | "80C" | `sys: {temperature '80', temperature_unit: 'celsius'` |
| `sys.time` | | "3 pm tomorrow" | `sys: {time: '2020-12-25T15:00:00.000+00:00', time_grain: 'hour'}` |
| `sys.url` | Checks if the given input is a URL. Accepted formats can be with www (*[www.chatlayer.ai](http://www.chatlayer.ai)*) or without (*chatlayer.ai*). Just the domain 'chatlayer' will not be accepted. | "[www.chatlayer.ai/jobs](https://www.chatlayer.ai/jobs)" | `sys: {url: 'www.chatlayer.ai/jobs', url_domain: 'chatlayer.ai'}` |
| `sys.duration` | | "3 hours" | `sys: {duration: '3', duration_unit: 'hour', duration_normalized: '10800', duration_normalized_unit: 'second'}` |
{% hint style="warning" %}
You should never overwrite System Entities yourself – they are automatically overwritten by the last detected variable (if any values are detected). So instead, save the System Entity to a [variable](/navigation/settings/secure-variables-gdpr.md) of your own choosing outside the `sys` or `internal` namespaces.
{% endhint %}
## Use system entities
To use system entities in your bot:
1. Create a [**Collect input**](/buildabot/flow-logic/dialog-state/user-input-bot-dialog.md) block. For instance, make it as a block that asks for the user email.
{% hint style="danger" %}
Please note that the number of system entities that you can use inside a **Collect input** block is limited. The system entities that you can use inside those blocks are: **sys.email**, **sys.phone\_number**, **sys.url**, **sys.number**, and **sys.time**.
{% endhint %}
2. Under **Capture use response as**, scroll down until you find the list of **System entities**.
3. Select the system entity of your choice. For this example, we would select `@sys.email`.
Select a system entity.
4. Under **Save variable as**, choose a variable to store the entity value.
Save the system entity value into a variable
4. Click **Save**.
---
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