Periods

You already know how to use periods. That’s not the same thing as understanding how they work.

Using punctuation vs. understanding punctuation

Knowing how to use something isn’t the same as understanding how it works. On the ACT, you need to know what each punctuation mark does grammatically.

For example, you might know how to use a computer without knowing how the electronics inside it work. In the same way, you might know how to type and send a text message without understanding the technology that moves that message from your phone to someone else’s.

Understanding punctuation on the ACT

To do well on ACT English, you need more than “what looks right.” You need the rules for each punctuation mark. When you know the rules, you can answer punctuation questions consistently.

Let’s start with a definition of the period: a period is a punctuation mark used to end a declarative sentence (a sentence that declares something). If a sentence isn’t declaring something, it may be asking something instead, and that usually requires a different punctuation mark.

Definitions

Period

A punctuation mark used to end a declarative sentence

ACT period checklist

Since you probably already use periods correctly in everyday writing, focus now on the rule the ACT tests: using a period correctly depends on knowing what a complete sentence is.

Here’s a checklist you can use to decide whether what you’re reading is a complete sentence. You need three things to have a complete sentence:

1. Subject
2. Verb
3. Complete Thought

Example

Walking slowly, the policeman kept a sharp eye.

The subject-verb pair here is “policeman-kept” because “kept” is the action and “policeman” is the person doing it.

You might mistake “walking” for the main verb, but notice that it doesn’t have its own subject. “Policeman” can’t be the subject of “walking” here because it’s already paired with “kept.”

Because the sentence has a subject, a verb, and a complete thought, it can end with a period.

Using the period to connect sentences

Here is the period rule you’ll see most often on the ACT:

Periods connect complete sentences.

Let’s walk through an example.

Example

Let’s say you have two sentences you want to connect.

Sentence 1: He likes red

Sentence 2: She likes blue

If you put a period between them, you connect the two sentences like this:

He likes red. She likes blue.

On ACT English, you’ll often choose the correct punctuation to connect sentences.

This seems simple, but the test often tries to make an incomplete sentence look complete.

Period trap

The ACT English test will try to trick you into thinking something is a sentence when it isn’t.

Here’s an example of how the ACT English Test will try and trick you.

Example

While I can’t stand politics during the presidential elections. I love the memes that come from it.

1. NO CHANGE
2. elections, I

You’re choosing between a period and a comma. Even though you haven’t learned comma rules yet (you’ll learn them in the chapter Linking dependent clauses), you don’t need them to answer this question.

All you have to do is use the checklist.

ACT tip

You need three things to have a complete sentence:

1. Subject
2. Verb
3. Complete Thought

This example contains two clauses (a clause is a clump of text with a subject and a verb). The key question is: Are both clauses complete sentences? If they are, you can use a period. If one isn’t, you can’t.

Clause 1: While I can’t stand politics during the presidential elections

Clause 2: I love the memes that come from it

Let’s test Clause 1 using the complete sentence checklist.

1. Subject: Does Clause 1 have a subject?

2. Verb: Does Clause 1 have a verb?

3. Complete Thought: Does Clause 1 express a complete thought?

A clause must meet all three points on the checklist to be a sentence. Since Clause 1 is not a complete sentence, you can’t put a period after it.

See if you can answer the following question by yourself.

Exercise

There are hundreds of millions of stars in our galaxy. Our sun is just one of them.

A. NO CHANGE
B. galaxy, our

Pick the correct answer using the sentence checklist.

Use the sentence checklist whenever you’re deciding whether a period is correct.

Key points

You need three things to have a complete sentence:

1. Subject
2. Verb
3. Complete Thought