how to make a scss variable

1$color-black: #000000;
2
3body {
4    --color: #{$color-black};
5}

1$myFont: Helvetica, sans-serif;
2$myColor: red;
3$myFontSize: 18px;
4$myWidth: 680px;
5
6body {
7  font-family: $myFont;
8  font-size: $myFontSize;
9  color: $myColor;
10}
11
12#container {
13  width: $myWidth;
14}

1$variableName = item
2
3$gray = #404040
4
5body{
6	background:$gray; 
7}