* [`==` and `!=`](/documentation/operators/equality) are used to check if two values are the same. * [`+`, `-`, `*`, `/`, and `%`](/documentation/operators/numeric) have their usual mathematical meaning for numbers, with special behaviors for units that matches the use of units in scientific math. * [`<`, `<=`, `>`, and `>=`](/documentation/operators/relational) check whether two numbers are greater or less than one another. * [`and`, `or`, and `not`](/documentation/operators/boolean) have the usual boolean behavior. Sass considers every value "true" except for `false` and `null`. * [`+`, `-`, and `/`](/documentation/operators/string) can be used to concatenate strings. {% if parens %} * [`(` and `)`](/documentation/operators#parentheses) can be used to explicitly control the precedence order of operations. {% endif %}