^title Variables Variables are named slots for storing values. You define a new variable in Wren using a `var` statement, like so:

var a = 1 + 2

This creates a new variable `a` in the current scope and initializes it with the result of the expression following the `=`. Once a variable has been defined, it can be accessed by name as you would expect.

var animal = "Slow Loris"
System.print(animal) //> Slow Loris

## Scope Wren has true block scope: a variable exists from the point where it is defined until the end of the [block](syntax.html#blocks) where that definition appears.

{
  System.print(a) //! "a" doesn't exist yet.
  var a = 123
  System.print(a) //> 123
}
System.print(a) //! "a" doesn't exist anymore.

Variables defined at the top level of a script are *top-level* and are visible to the [module](modules.html) system. All other variables are *local*. Declaring a variable in an inner scope with the same name as an outer one is called *shadowing* and is not an error (although it's not something you likely intend to do much).

var a = "outer"
{
  var a = "inner"
  System.print(a) //> inner
}
System.print(a) //> outer

Declaring a variable with the same name in the *same* scope *is* an error.

var a = "hi"
var a = "again" //! "a" is already declared.

## Assignment After a variable has been declared, you can assign to it using `=`:

var a = 123
a = 234

An assignment walks up the scope stack to find where the named variable is declared. It's an error to assign to a variable that isn't defined. Wren doesn't roll with implicit variable definition. When used in a larger expression, an assignment expression evaluates to the assigned value.

var a = "before"
System.print(a = "after") //> after

If the left-hand side is some more complex expression than a bare variable name, then it isn't an assignment. Instead, it's calling a [setter method][]. [setter method]: method-calls.html#setters

Functions → ← Control Flow