Punctuation — Core Skills

Punctuation: The Basics

Part 1 of 2 — One Question to Ask Every Time

Punctuation questions on the SAT look like they are about commas and semicolons. They are really about one thing: where does one sentence stop and the next one start?

First, a word we will use: clause

A clause is a group of words with a subject and a verb.

• The subject is who or what the sentence is about.
• The verb is what they do or are.

A clause that can stand alone as its own sentence is called independent. "The bus was late" is independent. It has a subject (the bus), a verb (was), and it makes sense by itself.

The rule

Two independent clauses cannot be glued together with only a comma.

Look at this:

The bus was late, we missed the movie.

"The bus was late" is a complete sentence. "We missed the movie" is a complete sentence. A comma is too weak to hold two complete sentences together. This mistake has a name: a comma splice.

Three ways to fix it

1. Period. The bus was late. We missed the movie.
2. Semicolon. The bus was late; we missed the movie.
3. Comma plus a joining word. The bus was late, so we missed the movie.

All three are correct. The SAT usually gives you only one of them in the answer choices, so you pick whichever one shows up.

The joining words that work in option 3 are for, and, nor, but, or, yet, so. Many students remember them as FANBOYS.

Your move

When you see a punctuation question, cover the answer choices. Read the words on the left of the blank and ask: could that be its own sentence? Then read the words on the right and ask the same thing. If the answer is yes both times, you need a period, a semicolon, or a comma plus a FANBOYS word — never a comma alone.

Punctuation: Practice

Part 2 of 2 — Your Checklist

Part 1 covered joining two complete sentences. Here are three more patterns that show up again and again, plus a checklist you can run on any punctuation question.

1. A comma after an opening phrase

When a sentence starts with a short lead-in before the main idea, put a comma at the end of that lead-in.

Before the game, we ate pizza.

The comma marks where the lead-in stops and the main sentence starts.

2. A colon needs a complete sentence on its LEFT

A colon (:) says "here it comes." It can introduce a list or an explanation. But the words before the colon must be able to stand alone as a sentence.

I packed three things: a hat, a map, and water.

"I packed three things" is a complete sentence, so the colon is allowed. Compare that to "I packed: a hat, a map, and water." Here "I packed" is not doing the job, because the colon has cut the sentence in half.

3. Extra information gets a comma on BOTH sides

Sometimes a sentence drops in a detail you could remove without breaking the sentence. That detail is called a supplement — extra information. It needs the same mark on both sides: comma...comma.

My uncle**,** who lives in Texas**,** sends postcards.

Take out "who lives in Texas" and you still have "My uncle sends postcards." That is the test. One comma without its partner is wrong.

Your checklist

1. Cover the answer choices.
2. Is there a complete sentence on the left of the blank? On the right?
3. Two complete sentences → period, semicolon, or comma + FANBOYS. Never a comma alone.
4. Opening lead-in phrase → comma at the end of it.