How to define variable in LESS ?

Less allows variables to be defined. Less variables are defined with an at sign(@). Variable assiment is done with a Colon (:).

During translation, the values of the variables are inserted into the output CSS document.

@varcolor: #ccc;
 
#header {
  color: @varcolor;
}
h2 {
  color: @varcolor;
}

The code above in Less would compile to the following CSS code.

#header {
  color: #ccc;
}
h2 {
  color: #ccc;
}