> For the complete documentation index, see [llms.txt](https://osl.mistium.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://osl.mistium.com/the-language/defining-variables.md).

# Defining Variables

Use `name = value` to create or update an untyped variable.

```javascript
variable = 10
```

Top-level variables are global and can be read inside functions:

```javascript
greeting = "hello"

def showGreeting() (
  log greeting
)

showGreeting()
// hello
```

Inside a function or block, declare local variables with a type keyword or `auto`. Local variables shadow globals with the same name and do not leak out of the function.

```javascript
any count = 1

def increment() (
  any count = 10
  count += 1
  log count
)

increment()
log count
// 11
// 1
```

Variables must be assigned or declared before they are read. Referencing an undefined variable is an error in current OSL.