Nesting Selectors

Sass can nest selectors.
#main {
  width: 97%;

  p, div {
    font-size: 2em;
    a { font-weight: bold; }
  }

  pre { font-size: 3em; }
}

#main {
  width: 97%;
}
#main p, #main div {
  font-size: 2em;
}
#main p a, #main div a {
  font-weight: bold;
}
#main pre {
  font-size: 3em;
}