Mermaid's syntax is used to create diagrams. You'll find that it is not too tricky and can be learned in a day. The next sections dive deep into the syntax of each diagram type.
Diagram Examples can be found in the [Mermaid Live Editor](https://mermaid-js.github.io/mermaid-live-editor), it is also a great practice area.
## Syntax Structure
One would notice that all **Diagrams definitions begin** with a declaration of the **diagram type**, followed by the definitions of the diagram and its contents. This declaration notifies the parser which kind of diagram the code is supposed to generate.
**Example** : The code below is for an Entity Relationship Diagram, specified by the `erDiagram` declaration. What follows is the definition of the different `Entities` represented in it.
```
erDiagram
CUSTOMER }|..|{ DELIVERY-ADDRESS : has
CUSTOMER ||--o{ ORDER : places
CUSTOMER ||--o{ INVOICE : "liable for"
DELIVERY-ADDRESS ||--o{ ORDER : receives
INVOICE ||--|{ ORDER : covers
ORDER ||--|{ ORDER-ITEM : includes
PRODUCT-CATEGORY ||--|{ PRODUCT : contains
PRODUCT ||--o{ ORDER-ITEM : "ordered in"
```
```mermaid
erDiagram
CUSTOMER }|..|{ DELIVERY-ADDRESS : has
CUSTOMER ||--o{ ORDER : places
CUSTOMER ||--o{ INVOICE : "liable for"
DELIVERY-ADDRESS ||--o{ ORDER : receives
INVOICE ||--|{ ORDER : covers
ORDER ||--|{ ORDER-ITEM : includes
PRODUCT-CATEGORY ||--|{ PRODUCT : contains
PRODUCT ||--o{ ORDER-ITEM : "ordered in"
```
The [Getting Started](./n00b-gettingStarted.md) section can also provide some practical examples of mermaid syntax.
One should **beware the use of some words or symbols** that can break diagrams. These words or symbols are few and often only affect specific types of diagrams. The table below will continuously be updated.
|[`%%{``}%%`](https://github.com/mermaid-js/mermaid/issues/1968) | Similar to [Directives](./directives.md) confuses the renderer.|In comments using `%%`, avoid using "{}".|
| **Flow-Charts** | | |
|'end' | The word "End" can cause Flowcharts and Sequence diagrams to break | Wrap them in quotation marks to prevent breakage.|
| [Nodes inside Nodes](https://mermaid-js.github.io/mermaid/#/flowchart?id=special-characters-that-break-syntax)| Mermaid gets confused with nested shapes | wrap them in quotation marks to prevent breaking|
### Mermaid Live Editor
Now, that you've seen what you should not add to your diagrams, you can play around with them in the [Mermaid Live Editor](https://mermaid-js.github.io/mermaid-live-editor).
# Configuration
Configuration is the third part of Mermaid, after deployment and syntax. It deals with the different ways that Mermaid can be customized across different deployments.
If you are interested in altering and customizing your Mermaid Diagrams, you will find the methods and values available for [Configuration](./Setup.md) here. It includes themes.
This section will introduce the different methods of configuring the behaviors and appearances of Mermaid Diagrams.
The following are the most commonly used methods, and they are all tied to Mermaid [Deployment](./n00b-gettingStarted.md) methods.
Allows for the limited reconfiguration of a diagram just before it is rendered. It can alter the font style, color and other aesthetic aspects of the diagram. You can pass a directive alongside your definition inside `%%{ }%%`. It can be done either above or below your diagram definition.
An application of using Directives to change [Themes](./theming.md). `Theme` is a value within Mermaid's configuration that dictates the color scheme for diagrams.