sass-site/source/_includes/doc_snippets/truthiness-and-falsiness.liquid

{% markdown %}
  ## Truthiness and Falsiness

  Anywhere `true` or `false` are allowed, you can use other values as well. The
  values `false` and [`null`][] are *falsey*, which means Sass considers them to
  indicate falsehood and cause conditions to fail. Every other value is considered
  *truthy*, so Sass considers them to work like `true` and cause conditions to
  succeed.

  [`null`]: /documentation/values/null

  For example, if you want to check if a string contains a space, you can just
  write `string.index($string, " ")`. The [`string.index()` function][] returns
  `null` if the string isn't found and a number otherwise.

  [`string.index()` function]: /documentation/modules/string#index
{% endmarkdown %}

{% headsUp %}
  Some languages consider more values falsey than just `false` and `null`. Sass
  isn't one of those languages! Empty strings, empty lists, and the number `0` are
  all truthy in Sass.
{% endheadsUp %}