Here's a breakdown:
* Independent Clause: A complete thought that can stand alone as a sentence.
* Dependent Clause: A group of words that contains a subject and verb but cannot stand alone as a sentence. It relies on the independent clause for its meaning.
Examples:
Comma needed:
* The weather was terrible, so we decided to stay inside. ("So we decided to stay inside" is a dependent clause that relies on the independent clause "The weather was terrible" for its meaning.)
* I studied hard for the exam, so I was confident in my abilities. ("So I was confident in my abilities" is a dependent clause.)
* He was exhausted, so he went to bed early. ("So he went to bed early" is a dependent clause.)
Comma not needed:
* I am so tired. ("So tired" is not a dependent clause.)
* She is so smart. ("So smart" is not a dependent clause.)
* They were so excited. ("So excited" is not a dependent clause.)
Key Point: If "so" is followed by a complete thought that can stand alone as a sentence, then you don't need a comma.
Additional Notes:
* There are rare cases where "so" might be used in a different way and a comma may be needed. However, the above rule covers the majority of instances.
* If you are unsure whether to use a comma before "so," read your sentence aloud. If it sounds natural to pause before "so," then a comma is likely needed.