how to declare var in scss use in other scss file code example

Example 1: SCSS variables

$font-stack:    Helvetica, sans-serif;
$primary-color: #333;

body {
  font: 100% $font-stack;
  color: $primary-color;
}

Example 2: how to make a scss variable

$variableName = item

$gray = #404040

body{
	background:$gray; 
}