A writer can get by in most circumstances with only the most basic punctuation. Periods need to follow declarative sentences, question marks follow questions, exclamation points follow excited or shouted sentences, and quotation marks go around quotes and dialogue. Aside from these, the only other piece of punctuation that is absolutely essential in English is the comma. Without commas, sentences would all be simple and repetitive.

Example 1: “Frequently, before the child has reached its twelfth month, its mother is taken from it, and hired out on some farm a considerable distance off, and the child is placed under the care of an old woman, too old for field labor.” – The Narrative of the Life of Frederick Douglass by Frederick Douglass

Imagine this example without commas.

Example 2: A child is frequently taken from its mother before it has reached its twelfth month. It is hired out on some farm a considerable distance off. The child is placed under the care of a woman who is too old for field labor.

This is much choppier than the first example. It doesn’t flow. It would get very annoying if an entire book were written without commas. Commas are important.

Some people (including some English instructors) make the rules for commas seem overly-complicated, but they needn’t be. The truth is that there are two simple rules for commas that cover 90% of their uses.

Rule 1: Use a comma between an independent and dependent clause.

Example 1: “This picture brought such an agony of pleasurable suffering that he worked it over and over again in his mind and set it up in new and varied lights, till he wore it threadbare.” – The Adventures of Tom Sawyer by Mark Twain

Independent clauses are those that could be a sentence by themselves and dependent clauses are those that rely on an independent clause to make sense. In this example the clause, “till he wore it threadbare,” does not make sense by itself. It depends upon the sentence that it is attached to for its meaning.

Example 2: “Cardiff Hill, beyond the village and above it, was green with vegetation and it lay just far enough away to seem a Delectable Land, dreamy, reposeful, and inviting.” – The Adventures of Tom Sawyer by Mark Twain

The sentence would still be complete without the phrase “beyond the village and above it” and this dependent clause only makes sense in the context of the rest of the sentence. We call particular type of dependent clause a “parenthetical expression” because it can also be denoted using parentheses or em-dashes. Commas are also used in this example to separate three adjectives describing the land, “dreamy, reposeful, and inviting,” which brings us to rule 2.

Rule 2: Use commas to separate items in a list.

There is always some debate about the final comma in a list (called the “Oxford” or “serial” comma), but the safest bet is to always include it. Most of the time it doesn’t matter, but there are a few occasions where a lack of a final comma can cause confusion or ambiguity. In fact, in 2018, a company in Maine lost a $5 million lawsuit due to a missing Oxford comma.