In your own words, explain when a comma is necessary to set apart a subordinate clause and when it is not. Provide a sample sentence to illustrate the rule.

When the sentence is inverted, meaning that the subordinate clause comes before the independent one, then you have to use a comma. For example:

Before I could stop her, she took one of my cookies.

On the other hand, if the subordinate clause follows the independent one, a comma is unnecessary. For example:

I wanted to get home before my parents arrived.

In both examples, the subordinate clause is underlined.