Edit in JSFiddle

/*MIXIN: declaration fornt styling*/
@mixin myappFont($fontfamily,$fontsize,$fontcolor,$fontweight) {
  font-family: left;
  font-size:$fontsize;
  color:$fontcolor;
  font-weight:$fontweight;
}

thead th{
    /*Calling the MIXIN myappFont*/
    @include myappFont(georgia,10px,red,400);
}

tbody td{ 
    /*Calling the MIXIN myappFont*/
   @include myappFont(arial,12px,blue,600);    
}