We use the conjunction unless to mean 'except if'. The clause which follows unless is a subordinate clause (sc): it needs a main clause (mc) to make a complete sentence. When unless comes before the main clause, we use a comma: Unless [SC]it rains, [MC]we'll go for a picnic by the river tomorrow.
How do you use unless in a sentence?
Use unless with present tenses when talking about the future.
- Present. You will damage your health unless you stop smoking. = you will damage your health if you do not stop smoking.
- Past. Unless she was working late, she would be here. ...
- Past Perfect. I wouldn't have taken Paul unless his car hadn't broken down.
Should a comma come before than?
A comma should not be placed before “than” unless it appears in series. ... However, a comma must not be used before “than” when it ordinarily and non-parenthetically functions as a preposition or a conjunction in a sentence.
