When should I use "that" instead of "which" for clarity?

Use "that" when the information is necessary to identify the noun, as in "the book that I lost," because removing it makes the sentence unclear or changes its meaning entirely.

Is "which" better than "that" for formal writing?

No, "which" is not inherently better for formal writing; the correct choice depends on whether the clause is restrictive, where "that" is preferred, or non-restrictive, where "which" is standard.

Does using "which" cost more in terms of sentence complexity?

Yes, using "which" often adds a comma and extra words, increasing sentence length and complexity, whereas "that" creates a tighter, more direct structure that is simpler to parse.

What are the safety risks of misusing "that" and "which" in technical documents?

Misusing "that" and "which" in technical documents creates ambiguity, which can lead to misinterpretation of safety instructions, potentially causing operational errors or compliance failures in regulated industries.

Are "that" and "which" compatible with all types of relative clauses?

No, "that" is incompatible with non-restrictive clauses and cannot follow a comma, while "which" is incompatible with restrictive clauses that refer to people, where "who" or "that" is required.

What is the most common beginner mistake with "that" and "which"?

The most common beginner mistake is using "which" for restrictive clauses without commas, such as "the car which is red," which incorrectly implies there are multiple cars and the red one is incidental.

Can I switch "that" and "which" in a sentence without changing the meaning?

No, you cannot switch "that" and "which" without changing the meaning, because swapping them alters whether the clause is essential, thereby shifting the sentence's focus and the reader's interpretation.

How do "that" and "which" work in a real-world example like product descriptions?

In product descriptions, "that" specifies a unique feature, such as "the laptop that has 16GB RAM," while "which" adds a parenthetical detail, like "the laptop, which is silver," to describe without restricting.

Can I switch from "which" to "that" in a sentence that already has commas?

No, you cannot switch from "which" to "that" in a sentence with commas, because commas signal a non-restrictive clause, and "that" cannot introduce a non-restrictive clause, so the commas must be removed first.

Difference Between

Difference Between That and Which

Written byNex Virox Team

Editorial Team

Reviewed byVarshal Nirbhavane

Senior SEO & Organic Growth Professional · 5+ years

Published: September 2, 202619 min read

Quick answer

The main difference between That and Which is that That introduces a restrictive clause essential to meaning, while Which introduces a non-restrictive clause adding extra detail. That is used without commas to define the noun, while Which is used with commas to provide non-essential information.

Key takeaways

Core distinction: "That" introduces essential clauses; "which" introduces nonessential clauses set off by commas.
How each works: "That" restricts meaning and identifies the specific noun; "which" adds extra, removable information.
Punctuation rule: Use "which" with commas before it; use "that" with no commas in restrictive phrases.
Best-fit use case: Choose "that" for defining sentences like "the book that I read"; choose "which" for asides.
Most common mistake: Omitting commas with "which" or using "which" for essential clauses changes sentence meaning.

Table of Contents18 sections

Difference Between That and Which: Comparison Table

Aspect	That	Which
Definition	A relative pronoun introducing restrictive clauses that identify a specific noun.	A relative pronoun introducing non-restrictive clauses that add extra, non-essential information.
Core Purpose	Defines which specific person or thing is meant, narrowing the noun's identity.	Adds a descriptive comment about a noun already fully identified by context.
Clause Type	Introduces restrictive (essential) clauses that cannot be removed without changing meaning.	Introduces non-restrictive (non-essential) clauses that can be removed without altering core meaning.
Punctuation	Used without commas, integrating the clause directly into the sentence flow.	Always set off with commas, one before and one after the clause.
Removal Test	Deleting the clause changes the sentence's meaning or makes it illogical.	Deleting the clause leaves a grammatically complete sentence with unchanged meaning.
Sentence Structure	Creates a single, tightly bound noun phrase with no internal pauses.	Creates a main clause plus a parenthetical aside separated by comma pauses.
Information Weight	Carries essential identifying information that distinguishes one item from others.	Carries supplementary detail, often opinion, explanation, or background, not identification.
US Usage	Preferred for all restrictive clauses in formal American English writing.	Reserved almost exclusively for non-restrictive clauses in American English.
UK Usage	Commonly used for restrictive clauses, though which also appears there.	Frequently used for both restrictive and non-restrictive clauses in British English.
Formality Level	Neutral formality, appropriate for technical manuals, news, and casual writing alike.	Often signals a more formal or literary tone, especially in non-restrictive use.
Ambiguity Risk	Eliminates ambiguity by precisely specifying which noun among multiple options is meant.	Creates ambiguity in British English where it can introduce either clause type.
Reading Speed	Produces faster comprehension because no comma pause interrupts the noun-verb flow.	Slows reading slightly due to mandatory comma breaks around the inserted clause.
Clause Length	Handles short, medium, or long restrictive clauses without punctuation adjustments.	Works best with shorter asides; very long non-restrictive clauses become unwieldy.
Preposition Use	Typically appears without a preceding preposition; the preposition stays at clause end.	Often follows a preposition like in, of, or to, forming phrases such as in which.
Grammar Rules	Governed by strict restrictive-clause rules; that never takes a comma before it.	Governed by non-restrictive rules; which always requires paired commas in this role.
Style Guides	Mandated for restrictive clauses by Chicago Manual of Style and APA Style.	Mandated for non-restrictive clauses by Chicago, APA, and MLA style guides.
Relative Pronoun Role	Functions only as a restrictive relative pronoun, never for questions or non-essential clauses.	Functions as a non-restrictive relative pronoun, an interrogative, and a restrictive pronoun.
Noun Modification	Modifies a specific noun within a larger set, singling out one member of that set.	Modifies an entire clause or a unique noun that needs no further identification.
Clause Position	Appears immediately after the noun it modifies, with no separating punctuation.	Appears after the noun or clause, always enclosed by commas or a preceding comma.
Error Frequency	Rarely misused; errors occur mainly when writers insert a comma before that.	Frequently misused when writers omit commas or use which for restrictive clauses.
Teaching Priority	Taught first in ESL curricula as the default relative pronoun for essential information.	Taught later, after students master restrictive clauses, due to comma complexity.
Clarity Impact	Maximizes clarity by forcing the reader to attach the clause to the exact noun.	Reduces clarity slightly because the comma pause can detach the clause from its referent.
Spoken Usage	Dominates everyday speech for restrictive clauses; speakers rarely use which in conversation.	Appears rarely in casual speech, mostly in formal presentations or prepared remarks.
Typical Example	The car that has the sunroof is mine, identifying one car among several.	The car, which has a sunroof, is mine, adding a detail about an already known car.
Common Error	Writers incorrectly add a comma before that, creating a comma splice error.	Writers incorrectly omit commas around which, creating a run-on non-restrictive clause.
Typical Users	Preferred by journalists, technical writers, and editors following US style conventions.	Preferred by literary authors, British writers, and formal essayists for elegant asides.
Limitation	Cannot introduce non-restrictive clauses, so it fails when extra, removable detail is needed.	Cannot signal essential identification clearly in US English, so it fails for restrictive clauses.
Compatibility	Compatible with all noun types, including people, objects, and abstract concepts.	Compatible with objects and concepts, but stylistically awkward for referring to people.
Best-Fit Scenario	Best for instructions, specifications, and any sentence where the noun must be precisely identified.	Best for descriptive prose, commentary, and sentences where the noun is already unique.
Decision Rule	Choose that when removing the clause would change the sentence's core meaning.	Choose which when removing the clause leaves the sentence's meaning fully intact.

What Is That?

That is a relative pronoun used to introduce essential restrictive clauses. It identifies a specific noun by narrowing the meaning of a sentence. That exists to define which person, place, or thing you mean without adding optional or removable information.

Definition of That

That is a function word functioning as a relative pronoun that introduces a restrictive clause, which is a dependent clause providing information necessary to identify the antecedent. Removing this clause would alter the fundamental meaning of the sentence or render it incomplete or illogical.

Key Characteristics of That

Characteristic	What It Means in Practice
Restrictive only	It introduces information that is essential to identifying the noun it modifies.
No commas	Essential clauses never require commas separating them from the rest of the sentence.
Personal nouns	It can refer to people, groups, animals, or inanimate objects without any restriction.
Impersonal nouns	It is the preferred choice when referring to objects, concepts, and non-human entities.
Delimiting function	It restricts a general category to a specific subset within that broader category.
Full clause syntax	It always introduces a clause containing both a subject and a finite verb.
Object deletion	The pronoun can be omitted when it acts as the object of its own clause.
Preposition placement	Prepositions typically appear at the end of the clause rather than before the pronoun.
Formal neutrality	It is equally acceptable in formal writing, academic prose, and casual conversation.
No nonrestrictive use	It never introduces a clause that adds merely supplementary or parenthetical detail.

Common Examples of That

Google Search – a technology platform that indexes billions of web pages for queries.
Mona Lisa – a Renaissance painting that resides permanently in the Louvre Museum in Paris.
Amazon River – a waterway that carries the largest volume of water worldwide.
Airbus A380 – a double-deck aircraft that remains the largest passenger airliner ever built.
Democratic Party – a political organization that is one of two major US parties.
Python language – a programming language that emphasizes readability and simple syntax design.
Oxford Dictionary – a reference work that documents current English word usage extensively.
Mars rover – a robotic vehicle that explores the surface of the red planet scientifically.
Napoleon Bonaparte – a military leader that rose to dominate Europe during the nineteenth century.
Great Barrier Reef – a coral system that is the largest living structure visible from space.

Advantages and Limitations of That

Advantages	Limitations
Removes ambiguity by defining exactly which item among several you intend to discuss.	Cannot introduce nonessential information, so it fails for purely supplementary descriptive clauses.
Eliminates comma placement errors because essential clauses never take punctuation.	Overused in speech creates monotony compared to alternative relative clause constructions.
Works seamlessly for inanimate objects where the pronoun which feels overly formal or stilted.	Offers no stylistic variety when multiple relative clauses appear within a single paragraph.
Allows natural omission when functioning as the object, shortening sentences without losing clarity.	Confusing with demonstrative uses, leading to ambiguity about whether you mean this particular thing.
Simplifies sentence structure by merging two related ideas into one cohesive grammatical unit.	Repeated use across consecutive sentences produces heavy, bureaucratic prose that loses flow.
Universally accepted across all English dialects, formal registers, and international writing standards.	Provides no mechanism for adding evaluative commentary that is separate from core identification.
Creates strong cohesion by tightly binding the descriptive clause to its antecedent noun phrase.	Cannot be used with commas, which prevents setting off genuinely optional observations.
Supports precise technical and legal writing where precise identification is paramount.	Lacks a possessive form, forcing awkward rephrasing for clauses requiring ownership.
Functions effectively with collective nouns and groups where individual identity is not distinct.	Unavailable after prepositions in formal writing, limiting sentence construction flexibility.
Natural in spoken English, making it the default choice for everyday communication tasks.	Makes sentences longer; writers sometimes omit it unnecessarily, causing clarity problems later.

What Is Which?

Which is a relative pronoun that introduces a non-restrictive clause, adding extra, non-essential information about a noun. It exists to provide supplementary detail, set off by commas, without changing the core meaning of the sentence.

Definition of Which

Which is a relative pronoun used to introduce a subordinate clause that provides additional, non-essential information about a preceding noun or noun phrase, typically separated by a comma, and is never used to define or restrict the noun it modifies.

Key Characteristics of Which

Characteristic	What It Means in Practice
Non-restrictive clauses	Adds extra information that can be removed without changing the sentence's fundamental meaning.
Comma separation	Always requires a comma before the clause and a closing comma or period after it.
Refers to things	Used exclusively for objects, ideas, animals, or concepts, never for people.
Adds commentary	Provides author observations or side notes that are supplementary, not defining.
Follows prepositions	Appears after prepositions like "in," "for," or "about," which is grammatically correct.
Parenthetical function	Acts like an aside, giving the reader optional context or clarification.
No restrictive use	Never defines which specific item is meant; that role belongs to restrictive pronouns.
Formal tone	Common in academic, legal, and professional writing where precision matters.
Clause can be removed	Sentence remains grammatically complete and logical if the which-clause is deleted.
Often follows nouns	Directly follows the noun it describes, with a comma inserted between them.

Common Examples of Which

The Eiffel Tower – which attracts millions of visitors yearly, is a non-essential detail about the landmark.
Shakespeare's Hamlet – which was written around 1600, adds optional historical context to the play.
The Amazon Rainforest – which produces 20% of Earth's oxygen, offers supplementary environmental information.
Mount Everest – which stands at 8,849 meters, provides extra geographic data about the peak.
The Mona Lisa – which hangs in the Louvre, gives non-essential location details about the painting.
The Great Wall of China – which spans over 21,000 kilometers, adds optional measurement information.
The iPhone – which launched in 2007, provides extra historical background about the device.
The Roman Colosseum – which could hold 50,000 spectators, offers supplementary capacity details.
The Nile River – which flows through 11 countries, adds non-essential geographic information.
The Hubble Telescope – which orbits Earth, provides optional operational context about the instrument.

Advantages and Limitations of Which

Advantages	Limitations
Adds rich detail without cluttering the main sentence structure or confusing the reader.	Overuse creates wordy, bloated prose that slows reading speed and reduces clarity.
Allows writers to insert commentary or opinions naturally into factual statements.	Comma rules are frequently violated, leading to run-on sentences and grammatical errors.
Works correctly with prepositions, enabling sophisticated sentence constructions in formal writing.	Cannot be used for people, forcing writers to switch to "who" and breaking flow.
Signals to readers that information is optional, helping them prioritise key content.	Misused as a restrictive pronoun, causing ambiguity about which item is being referenced.
Enables complex, layered sentences that demonstrate advanced writing skill and nuance.	Creates distance between subject and verb, increasing risk of subject-verb agreement errors.
Provides a clear, standardised way to add parenthetical information in academic writing.	Frequently confused with "that," leading to incorrect punctuation and meaning shifts.
Maintains sentence integrity when clauses are removed, ensuring structural resilience.	Sounds overly formal or stilted in casual conversation, making speech feel unnatural.
Allows precise placement of supplementary details exactly where the reader needs them.	Cannot define or identify specific items, limiting its use in clarifying questions.
Supports parallel structure when multiple non-essential details are added to one noun.	Excessive use fragments writing, making paragraphs feel choppy and disconnected.
Enables elegant transitions between related ideas within a single, flowing sentence.	Requires careful comma placement that many writers find confusing or inconsistent.

Similarities Between That and Which

Shared Aspect	How That and Which Are Alike
Relative pronoun role	That and which both introduce restrictive relative clauses that identify a specific noun.
Clause connection	That and which both link a subordinate clause to a main clause in complex sentences.
Noun modification	That and which both modify nouns by adding essential identifying information about them.
Sentence position	That and which both appear directly after the noun they refer to in a sentence.
Formal writing use	That and which both appear frequently in academic, legal, and technical documents.
Informal speech use	That and which both occur naturally in everyday conversational English without confusion.
Subject replacement	That and which both can replace a subject pronoun like "who" or "whom" in some contexts.
Object replacement	That and which both can replace an object pronoun in a relative clause without changing meaning.
Zero relative option	That and which both can be omitted when they function as the object of a clause.
Punctuation rules	That and which both require no comma when they introduce essential clauses.
Grammar textbooks	That and which both receive dedicated sections in English grammar reference guides.
ESL learning focus	That and which both are taught as core relative pronouns in English language courses.
Writing style guides	That and which both appear in style manual examples for correct clause usage.
Sentence clarity	That and which both help readers understand which specific person or thing is meant.
Information density	That and which both allow writers to pack extra descriptive details into single sentences.
Antecedent agreement	That and which both agree with singular or plural antecedents without changing form.
Verb agreement	That and which both take verbs that match the number of their antecedent noun.
Preposition pairing	That and which both can follow prepositions like "in," "on," or "for" in formal writing.
Question formation	That and which both rarely start questions but appear in embedded question clauses.
Negation handling	That and which both work with negative verbs in relative clauses without issue.
Passive voice use	That and which both appear in passive-voice relative clauses equally well.
Active voice use	That and which both function identically in active-voice relative clauses.
Noun phrase head	That and which both attach to a head noun that serves as the clause's anchor.
Restrictive function	That and which both narrow the noun's meaning to a specific subset when essential.
Non-human reference	That and which both refer primarily to objects, ideas, animals, or concepts rather than people.
Collective noun use	That and which both modify collective nouns like "team" or "group" with singular verbs.
Abstract noun use	That and which both describe abstract nouns such as "idea," "theory," or "belief."
Concrete noun use	That and which both describe concrete nouns such as "book," "car," or "building."
Readability impact	That and which both improve sentence flow by avoiding repeated nouns or separate sentences.
Error frequency	That and which both are misused equally often by non-native speakers, showing similar difficulty.

That or Which: Which Should You Choose?

The single deciding variable is whether the information is essential or non-essential to the meaning of the sentence. If removing the clause changes the core meaning, use That. If the clause is just extra detail you could delete without losing the point, use Which with commas.

When to Use That

Choose That when the clause is essential to identify which person or thing you mean. Use it for restrictive clauses that narrow the noun down. If you remove the clause and the sentence becomes confusing or points to the wrong item, That is correct. No commas are used.

When to Use Which

Choose Which when the clause is non-essential and adds extra, removable information. Use it for parenthetical asides or descriptive details that do not change the noun's identity. If the sentence still makes complete sense when the clause is deleted, Which is correct. Always set it off with commas.

Common Misconceptions About That and Which

Common Myth	The Reality
That and which are completely interchangeable in every sentence.	That introduces essential clauses, while which introduces nonessential clauses, so swapping them changes the meaning of the sentence.
Which is always the more formal and correct choice.	That is the correct restrictive pronoun in American English; which is nonrestrictive and requires commas around its clause.
You can always omit that from a sentence without changing meaning.	Omitting that works in essential clauses, but which cannot be omitted because its nonessential clause needs the pronoun to stay attached.
British English uses which for everything, so the rules do not matter.	British English allows which for restrictive clauses, but that still works, and which nonrestrictive usage remains identical across both dialects.
Adding commas before which is optional and purely stylistic.	Commas before which are mandatory in American English because they signal the nonessential clause that follows the pronoun.
That can introduce a nonessential clause if you want extra detail.	That cannot introduce a nonessential clause; only which can, and that nonessential clause must be set off by commas.
Which is wrong to use for essential information in any dialect.	Which is acceptable for essential clauses in British English, though American style guides still prefer that for restrictive meaning.
The choice between that and which depends on whether you speak or write.	Spoken English often blurs the distinction, but written English requires that for essential clauses and which for nonessential ones.
That and which both refer only to objects, never to people.	That can refer to people or things, while which refers only to things, animals, or groups, never to individual persons.
You must always use which after a preposition like in or of.	That cannot follow a preposition directly, so which is required there, but that works when the preposition moves to the clause end.
Removing the clause introduced by that always destroys the sentence.	Removing a that clause destroys the sentence meaning, but removing a which clause leaves the main sentence fully intact and clear.
Which clauses never need commas when the sentence is short.	Which clauses always need commas regardless of sentence length because the comma marks the nonessential nature of the information.
That is informal slang, and which is the only proper written form.	That is standard formal English for essential clauses, and which is equally formal but reserved for nonessential clauses in American usage.
You can use that and which in the same sentence to mean the same thing.	Using that and which in one sentence creates two different clause types, so each pronoun must match its essential or nonessential role.
Which always introduces extra information that is not important to the reader.	Which introduces nonessential information, but that information can still be important; it is just not required to identify the noun.
That is only used in restrictive clauses, but which is only used in questions.	Which appears in questions and nonessential clauses, while that appears in essential clauses, so both serve multiple grammatical roles.
Putting a comma before that makes the sentence clearer and easier to read.	A comma before that is grammatically incorrect because that introduces an essential clause, which must never be separated by punctuation.
Which is always followed by a comma, but that is never followed by one.	Which is followed by a comma in nonessential clauses, while that takes no comma, but a comma can appear after the clause itself.
The difference between that and which is too subtle for most readers to notice.	Readers notice the difference because that identifies a specific noun, while which adds a parenthetical detail that commas visibly set apart.
You can replace which with that whenever you want a shorter sentence.	Replacing which with that changes a nonessential clause into an essential one, altering the meaning even if the sentence gets shorter.
That and which are relative pronouns that work identically after any noun.	That works after any noun for essential clauses, but which requires the noun to be definite or already identified for its nonessential clause.
Using which without commas is acceptable in casual emails or text messages.	Which without commas creates a grammatical error in any register, and readers will misinterpret the clause as essential rather than parenthetical.
That refers to something close, while which refers to something far away.	That and which do not indicate physical or temporal distance; that and this handle proximity, while which only marks clause type.
Grammar checkers always catch mistakes between that and which correctly.	Grammar checkers often miss which errors because they cannot judge whether a clause is essential, so manual review of meaning is required.
Which is the only pronoun you can use after a comma in a sentence.	That can follow a comma when the comma ends a preceding phrase, but that itself never takes a comma directly before it.
You should always choose which for longer sentences to sound more sophisticated.	Choosing which for long sentences creates nonessential clauses that add clutter, while that keeps essential information tight and direct.
That and which both introduce clauses that describe the noun right before them.	That and which both introduce relative clauses, but that clause identifies the noun, while which clause merely comments on the already-known noun.
If you remove a which clause, the sentence becomes ungrammatical and broken.	Removing a which clause leaves a complete grammatical sentence, which proves the clause was nonessential and correctly punctuated with commas.
You can use which to refer back to an entire previous sentence or idea.	Which can refer to a whole clause or idea, while that cannot do this, so which is the correct choice for sentence-level antecedents.
That and which are interchangeable when the noun is a thing like car or book.	That and which both work with things, but that restricts which car or book, while which adds a detail about an already specific car or book.

Conclusion

Difference Between That and Which hinges on restrictive versus nonrestrictive clauses. Use "that" for essential information defining the noun; omit commas. Use "which" for nonessential details adding extra context; set it off with commas. Rule: "that" restricts, "which" comments—choose accordingly for precise, clear writing.

FAQs on Difference Between That and Which

What is the difference between "that" and "which" in a sentence?: "That" introduces a restrictive clause, which is essential to the sentence's meaning, while "which" introduces a non-restrictive clause, adding extra information that can be removed without changing the core meaning.
When should I use "that" instead of "which" for clarity?: Use "that" when the information is necessary to identify the noun, as in "the book that I lost," because removing it makes the sentence unclear or changes its meaning entirely.
Is "which" better than "that" for formal writing?: No, "which" is not inherently better for formal writing; the correct choice depends on whether the clause is restrictive, where "that" is preferred, or non-restrictive, where "which" is standard.
Does using "which" cost more in terms of sentence complexity?: Yes, using "which" often adds a comma and extra words, increasing sentence length and complexity, whereas "that" creates a tighter, more direct structure that is simpler to parse.
What are the safety risks of misusing "that" and "which" in technical documents?: Misusing "that" and "which" in technical documents creates ambiguity, which can lead to misinterpretation of safety instructions, potentially causing operational errors or compliance failures in regulated industries.
Are "that" and "which" compatible with all types of relative clauses?: No, "that" is incompatible with non-restrictive clauses and cannot follow a comma, while "which" is incompatible with restrictive clauses that refer to people, where "who" or "that" is required.
What is the most common beginner mistake with "that" and "which"?: The most common beginner mistake is using "which" for restrictive clauses without commas, such as "the car which is red," which incorrectly implies there are multiple cars and the red one is incidental.
Can I switch "that" and "which" in a sentence without changing the meaning?: No, you cannot switch "that" and "which" without changing the meaning, because swapping them alters whether the clause is essential, thereby shifting the sentence's focus and the reader's interpretation.
How do "that" and "which" work in a real-world example like product descriptions?: In product descriptions, "that" specifies a unique feature, such as "the laptop that has 16GB RAM," while "which" adds a parenthetical detail, like "the laptop, which is silver," to describe without restricting.
Can I switch from "which" to "that" in a sentence that already has commas?: No, you cannot switch from "which" to "that" in a sentence with commas, because commas signal a non-restrictive clause, and "that" cannot introduce a non-restrictive clause, so the commas must be removed first.