how to declare a variable in sass

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

1$base-color: #c6538c;

1// SCSS variables
2
3$darkcolor: #605C4D;
4$large: 350px;
5
6section{
7	background-color: $darkcolor;
8  	height: $large;
9}

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
2$variablename: value;
3