var

Flash Player 5.

var variableName [= value1] [...,variableNameN [=valueN]]

variableName An identifier.

value The value assigned to the variable.

Nothing.

Statement; used to declare local or Timeline variables.

If you declare variables inside a function, the variables are local. They are defined for the function and expire at the end of the function call.
If variables are not declared inside a block ({}) but the action list was executed with a call() action, the variables are local and expire at the end of the current list.
If variables are not declared inside a block and the current action list was not executed with the call() action, the variables are interpreted as Timeline variables. However, you don't have to use var to declare Timeline variables.

You cannot declare a variable scoped to another object as a local variable:

my_array.length = 25;     // ok
var my_array.length = 25; // syntax error

When you use var, you can strictly type the variable; see Strict data typing

Note: Classes defined in external scripts also support public, private, and static variable scopes. See Creating Classes with ActionScript 2.0 and private, public, and static.