## Defining Responses

Responses go under the `responses` key in your domain file or in a separate "responses.yml" file. Each response name should start with `utter_`.
For example, you could add responses for greeting and saying goodbye under the response names `utter_greet` and `utter_bye`:

```yaml
domain.yml

intents:

- greet

responses:

utter_greet:

- text: "Hi there!"

utter_bye:

- text: "See you!"
```

If you are using [retrieval intents](https://legacy-docs-oss.rasa.com/docs/rasa/2.x/glossary#retrieval-intent) in your assistant, you also need to add responses for your assistant's replies to these intents:

```yaml
domain.yml

intents:

- chitchat

responses:

utter_chitchat/ask_name:

- text: Oh yeah, I am called the retrieval bot.

utter_chitchat/ask_weather:

- text: Oh, it does look sunny right now in Berlin.
```

##### note

Notice the special format of response names for retrieval intents. Each name starts with `utter_`, followed by the retrieval intent's name (here `chitchat`) and finally a suffix specifying the different response keys (here `ask_name` and `ask_weather`). See [the documentation for NLU training examples](https://legacy-docs-oss.rasa.com/docs/rasa/2.x/training-data-format#training-examples) to learn more.

### Using Variables in Responses

You can use variables to insert information into responses.
Within a response, a variable is enclosed in curly brackets. For example, see the variable `name` below:

```yaml
domain.yml

responses:

utter_greet:

- text: "Hey, {name}. How are you?"
```

When the `utter_greet` response is used, Rasa automatically fills in the variable with the value found in the slot called `name`. If such a slot doesn't exist or is empty, the variable gets filled with `None`.

Another way to fill in a variable is within a [custom action](https://legacy-docs-oss.rasa.com/docs/rasa/2.x/custom-actions).
In your custom action code, you can supply values to a response to fill in specific variables.
If you're using the Rasa SDK for your action server, you can pass a value for the variable as a keyword argument to [`dispatcher.utter_message`](/content/docs/action-server/sdk-dispatcher/index.html):

```python
dispatcher.utter_message(
    template="utter_greet",
    name="Sara"
)
```

If you use a [different custom action server](/content/docs/action-server#other-action-servers/index.html), supply the values by adding extra parameters to the responses your server returns:

```json
{
    "events": [],
    "responses": [
        {
            "template": "utter_greet",
            "name": "Sara"
        }
    ]
}
```

### Response Variations

You can make your assistant's replies more interesting if you provide multiple response variations to choose from for a given response name:

```yaml
domain.yml

responses:

utter_greet:

- text: "Hey, {name}. How are you?"

- text: "Hey, {name}. How is your day going?"
```

In this example, when `utter_greet` gets predicted as the next action, Rasa will randomly pick one of the two response variations to use.

### Channel-Specific Response Variations

To specify different response variations depending on which channel the user is connected to, use channel-specific response variations.
In the following example, the `channel` key makes the first response variation channel-specific for the `slack` channel while the second variation is not channel-specific:

```yaml
domain.yml

responses:

utter_ask_game:

- text: "Which game would you like to play on Slack?"
    channel: "slack"

- text: "Which game would you like to play?"
```

##### note

Make sure the value of the `channel` key matches the value returned by the `name()` method of your input channel. If you are using a built-in channel, this value will also match the channel name used in your `credentials.yml` file.

### Conditional Response Variations

Specific response variations can also be selected based on one or more slot values using a conditional response variation. A conditional response variation is defined in the domain or responses YAML files similarly to a standard response variation but with an additional `condition` key. This key specifies a list of slot `name` and `value` constraints.

When a response is triggered during a dialogue, the constraints of each conditional response variation are checked against the current dialogue state. If all constraint slot values are equal to the corresponding slot values of the current dialogue state, the response variation is eligible to be used by your conversational assistant.

### Rich Responses

You can make responses rich by adding visual and interactive elements. There are several types of elements that are supported across many channels:

#### Buttons

Here is an example of a response that uses buttons:

```yaml
domain.yml

responses:

utter_greet:

- text: "Hey! How are you?"
    buttons:
      - title: "great"
        payload: "/mood_great"
      - title: "super sad"
        payload: "/mood_sad"
```

Each button in the list of `buttons` should have two keys:

- `title`: The text displayed on the buttons that the user sees.
- `payload`: The message sent from the user to the assistant when the button is clicked.