# Rule

Each [message](https://app.gitbook.com/@docs-en-yoctol-ai/s/yoctol/~/edit/drafts/-LnQJsTXatUDJ-slOjKr/v/master/term-translations/message) on YOCTOL.AI has its own “rule”. Each rule defines a certain situation for the chatbot to react to the chatbot users’ input.

**There can only be one message connected to each rule.** \
**However, a message can have multiple rules.**

If you apply the same rule to multiple messages, the chatbot might not be able to reply correctly.

### Example

Take the message “Order information” as an example. The following examples are possible rules for the message.

1. NLU: Select the intent for “Order Information”
2. Keyword matching: Select “When it matches any keyword: ‘place an order’, ‘order drinks’ or ‘order’
3. Regular expression: write a regular expression such as “.\*(order|buy).\*$”. For more information about regular expressions, please visit [Regular Expression](https://app.gitbook.com/@docs-en-yoctol-ai/s/yoctol/~/edit/drafts/-LnQJsTXatUDJ-slOjKr/v/master/term-translations/regular-expression).

   <br>