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Commas before “Which” and “That”: Tricky Punctuation Explained

Whether you are a diligent student trying to uncover the secrets of grammar or a writer who does not want to be at fault, putting a comma before “which” and “that” can be complicated. To avoid embarrassing mistakes and show your academic proficiency, we have come up with a functional guide that will you help you out.

Three basic rules of using a comma before “which”

The basic rules of using a comma before “which” can be boiled down to these three points:

  • A comma is used before “which” in a nonrestrictive clause
  • A comma is never used before “which” in prepositional phrases
  • A comma is never used before “which” in indirect questions

Comma before “which” in nonrestrictive phrases

Before we start, it is important to define the meaning of a nonrestrictive phrase. A nonrestrictive phrase is a phrase that adds information to the context. However, the said information is not important or essential to the overall meaning of a sentence. For example:

  • ✔️ His new purchase, which attracted attention, stood in the parking lot.
  • ✔️ Their possessions, which were left in a drawer, had to be kept intact.

Nonrestrictive phrases are highlighted in yellow. As you can tell, a comma is required before “which” as well as at the end of the clause. So, how do you know this is a nonrestrictive phrase in the first place? The most rational way to prove it is to remove the phrase out of a sentence:

  • ✔️ His new purchase stood in the parking lot.
  • ✔️ Their possessions had to be kept intact.

The meaning of the sentences without nonrestrictive phrases remains the same. The writer is still discussing the purchase that has been made and the possessions that need to be kept intact. Below, you will read more examples of proper use of a comma before “which”:

Comma before “which"
This place, which is great to look at, is located in a friendly area.
His approach to an essay, which had a thrilling theme, surprised everyone.
Kate returned to her former job, which turned out to be a fantastic decision.
People loved the dedication, which was put into this motivational speech.

Comma before “which” in prepositional phrases

A comma is never used before “which” if it is a part of a prepositional phrase. You can read the correct and incorrect examples of the use of comma below:

❌Incorrect ✔️Correct
We saw three exits, the nearest of, which was painted red. ✔️ We saw three exits, the nearest of which was painted red.
The blankets in, which the cup was wrapped were embroidered with gold. ✔️ The blankets in which the cup was wrapped were embroidered with gold.
The rules on, which the test was based are known to everyone. ✔️ The rules on which the test was based are known to everyone.

How to use a comma before “that”

You only need a comma before “that” in case it is used as an introduction in the middle of the sentence. You can insert parenthesis that includes “that” regardless of the part of speech that it represents. Please note that the sentence may become incorrect in case “that” is used as a determiner or a pronoun.

“That” can also be used as an adverb in most sentences. There are cases when “that” can act as a conjunction. In the sentence where “that” connects a subordinate clause, the complex structure of the sentence is easier to analyze. “That” may also be classified as a relative pronoun in most essays. A relative pronoun in this case is linked to the already existing noun. To make sure that the comma is used correctly, think about the importance of putting “that” in a sentence.

Comma before “that” in a mid-sentence parenthesis

A parenthesis can be used as a word or a phrase in a sentence. It is also used with commas to construct the sentence properly. Once the comma is placed, the readers can analyze the message in the text and see the emphasized part of the context. Commas also facilitate the clarity of context. Once you set off the parenthetical remark with commas, you can add “that” to clarify the meaning:

  • ✔️ Lisa, that girl in the corner, is actually my brother’s best friend.
  • ✔️ Robert, that guy in the crowd, knows how to get to the entrance.

There is also a way of using “that” that includes the phrase “that is”, incorporated into a sentence. “That is” is a slightly less formal and short version of the phrase “that is to say”, which is commonly found in formal emails. To make the sentence sound more emphatic, “that is” can be set off with commas:

  • This book can be described as action-packed that is full of unexpected twists and turns.
  • ✔️ This book can be described as action-packed, that is, full of unexpected twists and turns.
  • The article is characterized as being overly sensitive that is displaying too little evidence.
  • ✔️ The article is characterized as being overly sensitive, that is, displaying too little evidence.

Comma before “that” in an end-sentence parenthesis

“That” can be used at the end of the sentence if it acts as a parenthesis. To display the further use of a comma in an academic context, here are other examples with “that” at the end of the sentence:

  • ✔️ He gave his money to the faithful family friend, that was what he was told.
  • ✔️ They felt that their apologies were not enough, that was what they were messaged.

Please note that the use of parentheses should not be limited to commas alone. In some cases, other punctuation devices can be used to add emphasis to the sentence:

  • ✔️ He gave his money to the faithful family friend (that was what he was told).
  • ✔️ They felt that their apologies were not enough (that was what they were messaged).

Using “that” as a pronoun

In some cases, “that” can take on the role of a pronoun in a sentence. Pronouns are usually used to indicate or replace a noun that separates two objects, seen from the writer’s viewpoint. A comma is never used before “that” in case it is a replacement for a demonstrative pronoun.

“That” may also become a determiner in a sentence. A determiner is a word that is placed before the noun. Determiners are often used in lists (this one, that one, and that one too). You can use a determiner “that” based on the following examples:

  • ✔️ I apologize for the intrusion, but I can’t get that invitation.
  • ✔️ Sorry for being honest, but I won’t accept that reasoning.

“That” is often found in informal speech. It acts as an emphatic adverb that means “very”. You can see some of the most common examples of the colloquial use of “that” below:

  • ✔️ These explanations are not that difficult to read.
  • ✔️ The rules are not that complicated to follow.

The nuances of speech can often leave you wondering about the best use of “which” and “that” in a sentence. You can amplify your knowledge of punctuation devices by studying grammar rules and memorizing the basic constructions you can later revise.

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