Commas with Which, That, and So

We’ve said this before but you’ll encounter commas on the ACT English test more than any punctuation.

Using a comma correctly depends on knowing a few situational comma rules. Since the comma has so many situational rules, the test makers are more likely to use them on the English ACT.

In addition to connecting clauses, commas get specific rules depending on the words that come before or after them.

Here’s what we mean.

The short answer is to use a comma before “which,” do not use a comma before “that,” and sometimes use a comma before “so,” but not when it means “so that.” Confused? Don’t worry, we’ll straighten it out.

These rules, understandably, confuse a lot of students. There are a lot of rules to keep track of and they often seem to overlap each other.

We’ve got you covered.

Keep reading to know exactly how to use commas with these words correctly.

Using commas with “which”

“Which” usually begins what’s called a nonrestrictive phrase, which (see what we did there?) is just a fancy word for a phrase that gives information that’s not essential to a sentence.

Therefore, like most sentence interruptions, we would have a comma before the “which.” Additionally, if that phrase ends before the end of the sentence, we would have a comma to close it.

Example

His denial didn’t tell the whole truth, which was that he knew who had done it.

I couldn’t believe what the doctor said, which was that there was no longer any trace of cancer.

Not using commas with “that”

“That” usually begins a restrictive phrase, which means it is essential to the sentence.

Since the phrase is essential to the sentence, we don’t put a comma before it.

Example

The man who was sitting next to me probably had COVID.

Notice here that it would be complicated to know which man had COVID.

In this sentence, we have to have “who was sitting next to me” to know what’s happening. If we didn’t have those words, it would be hard to tell which man in question had COVID.

Thus, the phrase “who was sitting next to me” is restrictive. Since it’s restrictive, we don’t have commas.

Sometimes using commas with “so”

The word “so” is tricky because it functions in two ways in the English language.

Sometimes, it’s a coordinating conjunction or FANBOYS that links two independent clauses (see the chapter FANBOYS and Joining Clauses).

Example

I learned to speak Japanese, so now I don’t use subtitles when watching anime.

In this case, we do need a comma before the word “so” because it’s linking two independent clauses.

• Independent Clause 1: I learned to speak Japanese
• Independent Clause 2: now I don’t use subtitles when I watch anime

To fuse the two independent clauses, we place a comma plus “so” between them.

Other times the word “so” comes before “that.” When this happens, we don’t need a comma.

Example

I dropped by the store on the way home so that I could grab some milk and bread before the snow.

Here, “so that” functions as a subordinating conjunction, which means we would NOT put a comma before it.

Yes, these rules may appear difficult. However, as long as you remember the three rules on test day, you should be in great shape.