# Dictionaries

Dictionaries are mutable, unordered collections of key-value associations. In a dictionary, all keys must have the same type, and all values must have the same type. Dictionaries may contain a key only once and may contain a value multiple times.

Dictionary literals start with an opening brace `{` and end with a closing brace `}`. Keys are separated from values by a colon, and key-value associations are separated by commas.

```
// An empty dictionary
//
{}

// A dictionary which associates integers with booleans
//
{
    1: true,
    2: false
}

// Invalid: mixed types
//
{
    1: true,
    false: 2
}
```