Understanding whether that introduces a restrictive or nonrestrictive clause is a fundamental part of mastering English grammar. When reading or writing sentences, many people wonder if that is always tied to restriction, or if it can also be used in a more flexible, descriptive way. The distinction between restrictive and nonrestrictive clauses affects not only the meaning of a sentence but also the punctuation and clarity. For writers, editors, students, and professionals alike, knowing how that operates grammatically helps avoid ambiguity and keeps communication precise.
Understanding Restrictive and Nonrestrictive Clauses
What Is a Restrictive Clause?
A restrictive clause (also called a defining clause) provides essential information about a noun. It narrows down the meaning so that the sentence cannot do without it. If the clause is removed, the meaning of the sentence changes significantly or becomes unclear. In English, these clauses are not separated by commas.
- Example: The bookthat has a red coveris mine.
In this case, that has a red cover tells us exactly which book is being referred to. Without this information, we wouldn’t know which book is being claimed.
What Is a Nonrestrictive Clause?
A nonrestrictive clause (also called a non-defining clause) adds extra, non-essential information to a sentence. You can remove it, and the core meaning of the sentence remains intact. These clauses are always set off with commas.
- Example: My book,which has a red cover, is on the table.
The phrase which has a red cover adds more detail, but we still know the speaker’s book is on the table, regardless of the color or any other description.
The Role of That in Clauses
Is That Used in Restrictive or Nonrestrictive Clauses?
In standard English grammar, that is used almost exclusively inrestrictive clauses. It introduces information that is necessary to the meaning of the sentence. On the other hand, which is used for nonrestrictive clauses. While in casual or conversational English the distinction is sometimes blurred, formal writing generally maintains the separation.
- Correct (restrictive): The shoesthat I bought yesterdayare already worn out.
- Incorrect (nonrestrictive with that): My shoes,that I bought yesterday, are already worn out.
- Correct (nonrestrictive): My shoes,which I bought yesterday, are already worn out.
So, that is not typically used in nonrestrictive clauses. This is an important distinction when deciding how to punctuate and how to structure your sentence.
Why the Distinction Matters
Clarity and Meaning
Choosing between restrictive and nonrestrictive clauses determines whether the reader sees the information as essential or additional. Misusing that or which can cause confusion or lead to misinterpretation of the intended meaning. For instance:
- The carsthat were parked outsidegot tickets. (Only those specific cars got tickets.)
- The cars,which were parked outside, got tickets. (All the cars were parked outside and all got tickets.)
Professional and Academic Writing Standards
In formal writing, adherence to the distinction between that and which is important for credibility and correctness. Style guides likeThe Chicago Manual of StyleandAPArecommend using that for restrictive clauses and which for nonrestrictive clauses. Breaking this rule might not render a sentence grammatically wrong, but it may be seen as less polished or careless in certain contexts.
Common Mistakes Involving That
Using That Instead of Which
One of the most frequent errors is using that when which is appropriate for nonrestrictive clauses. This mistake is often accompanied by incorrect comma usage.
- Incorrect: The museum, that opened last year, is already famous.
- Correct: The museum, which opened last year, is already famous.
Omitting That When It’s Needed
In some restrictive clauses, omitting that can make the sentence less clear or harder to understand, especially when the clause is long or complex.
- Less clear: The movie you recommended was excellent.
- Clearer: The moviethat you recommendedwas excellent.
While dropping that is sometimes acceptable in informal speech, including it often improves clarity in writing.
Exceptions and Flexible Usage
Situational Flexibility
Some modern style guides and linguistic studies recognize that in everyday spoken English, many people use which and that interchangeably. However, this does not mean it is acceptable in all contexts. Academic, business, and journalistic writing often demand precision and consistency. Therefore, it’s best to follow the traditional rules unless there’s a compelling reason not to.
Regional Variations
There may also be regional preferences. In British English, which is more commonly used even in restrictive clauses. American English tends to follow stricter guidelines separating that and which. For international communication, it’s safest to use that for restrictive and which for nonrestrictive.
Summary: Is That Restrictive or Nonrestrictive?
Key Takeaways
- That introducesrestrictive clauses, which are essential to the sentence’s meaning.
- Which introducesnonrestrictive clauses, which add extra, non-essential information.
- Restrictive clauses donotuse commas; nonrestrictive clauses do.
- Correct usage enhances clarity, professionalism, and grammatical accuracy.
- In formal writing, never use that to begin a nonrestrictive clause.
Understanding the difference between restrictive and nonrestrictive clauses, and knowing the correct use of that, improves both writing and comprehension. It helps prevent ambiguity and ensures that your sentences communicate exactly what you intend. While language does evolve, clarity remains a timeless priority, and using that correctly plays a crucial role in achieving it.