Do You Put a Comma Before and After “That Is”?

The importance of punctuation, particularly comma placement, cannot be overstated in English language. Comma usage can undeniably alter both the meaning and flow of a sentence. The focus of this article will be on the term "that is" and the implications of comma usage around it.

Understanding "That Is"

The term "that is" is a Latin abbreviation, "id est" (i.e.), used frequently in English writing. It is typically employed to clarify or elaborate on a preceding statement. Commonly, "that is" serves as a parenthetical expression, similar to terms like "for example" or "in other words". As a parenthetical, it provides non-essential, additional information to a sentence and is therefore often set off by commas.

Grammatically, "that is" functions as a conjunction, connecting the main clause of a sentence with a secondary one. This secondary clause usually provides additional information or clarification to the main clause. It's essential to understand that the conjunction "that is" acts as a bridge between two related thoughts within the same sentence.

General Rules for Comma Usage with "That Is"

When using "that is" in a sentence to elaborate or clarify, it is common practice to place a comma before and after the term. This gives the reader a clear indication that the information following "that is" is supplemental and helps to avoid confusion. It's important to note, however, that these commas can be omitted in informal writing or dialogue, as they may disrupt the flow.

There are exceptions to this rule. If the phrase "that is" appears at the beginning or end of a sentence, it is usually followed or preceded by a single comma. The same applies when "that is" is used in a restrictive sense, where the information it introduces is essential to the meaning of the sentence. In such cases, commas are generally omitted.

Examples in Context

In this section, we'll illustrate the various ways to use "that is" in sentences, with and without commas.

Without a comma

Sentence Correct/Incorrect Explanation
I have only one brother that is older than me. Correct "That is" is used in a restrictive sense, the information it introduces is essential.
The book that is on the table is mine. Correct "That is" is used to define which book, it's essential information.
The dog that is in the backyard belongs to my neighbor. Correct "That is" is used to specify the dog, hence it is essential.

With a comma

Sentence Correct/Incorrect Explanation
I love painting, that is, creating art with colors. Correct "That is" is used to elaborate on the term "painting".
She's moving to Paris, that is, if her visa is approved. Correct "That is" is used to add a conditional statement.
He's an excellent chef, that is, when he actually has time to cook. Correct "That is" is used to qualify the preceding statement.

Common Mistakes and How to Avoid Them

A common mistake is to neglect using commas with "that is" when the information it introduces is non-essential. This can make the sentence confusing to read. To avoid this, always remember to set off non-essential information with commas.

Another frequent error is using commas with "that is" when it's introducing essential information. This can disrupt the sentence's flow and make it seem like the information could be removed without altering the sentence's meaning. To avoid this, remember that essential information should not be set off by commas.

Comparing "That Is" with Other Similar Terms

A term that often gets confused with "that is" is "i.e.," which is actually the Latin abbreviation for "id est," the term's literal translation. Both are used to provide clarification or additional information in a sentence, but their usage differs slightly.

  • Both terms can be used interchangeably when introducing non-essential information.
  • "I.e." is typically used in more formal or academic writing, while "that is" can be used in both formal and informal contexts.

Quick Recap and Key Takeaways

We've explored the use of "that is" in English sentences and the importance of correct comma placement. Here's a quick summary of what we've learned:

  • "That is" is a conjunction used to provide additional information or clarification.
  • When introducing non-essential information, "that is" should be set off by commas.
  • When introducing essential information, "that is" should not be set off by commas.
  • The term "that is" can be swapped with "i.e." in most contexts, but "i.e." is generally more formal.

Remember, the key to mastering comma usage is practice and careful reading. With time, correct punctuation will become second nature.

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