Commas are incredibly important for many reasons. At the most basic level, commas make reading more digestible, giving space and rhythm between ideas within a complete sentence (see my comma use in this sentence alone.) Commas break up thoughts and separate dependent clauses from independent clauses. They introduce information, set apart appositives, distinguish list items from each other, and many other things. Plus, commas clarify if ideas are meant to be combined or separated. Just read the controversy on commas and the Second Amendment to see how some would argue that the comma gave Americans the right to own guns!
Comma Difficult Ranking: 1/14 (most difficult to master)
The comma seems relatively simple to use at first and it is, by far, the most widely used punctuation mark (outside of the period and question mark, of course.) But there are fourteen different ways to use commas, making it widely misused and relatively difficult to master. Be careful not to place commas where they shouldn’t be; avoid combining two complete sentences with a comma (which we call a comma splice); and always put commas where they should be to avoid confusion. If you can learn to master the fourteen uses of commas, you’ll be on your way to writing with clarity and precision and you’ll give your sentences some variety.