Comma Before Which: Grammar Guide

Demystifying Comma Before Which: A Comprehensive Grammar Guide for Word Nerds

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Derek Cupp

By Derek Cupp

If you’ve ever questioned the placement of a comma before “which” in your writing, you’re not alone. This seemingly small punctuation point can cause big confusion. Commas and their usage often stump even seasoned writers, especially when it comes to using them with words like “which”.

My aim here is to unravel this grammatical mystery once and for all. Let’s dive into the conundrum surrounding the use of a comma before “which”, busting some common myths, clarifying rules, and making sure your written communication shines.

So buckle up! We’re about to embark on an enlightening journey through grammar land where I’ll make it simple for you to understand when exactly that elusive comma should appear before “which”.

Understanding the Role of Commas in English Grammar

Commas, those tiny punctuation marks we often ignore, play a significant role in molding our sentences. They’re the unsung heroes of clarity and coherence in written English.

To understand their importance, let’s first define what a comma is. A comma is a punctuation mark used to separate elements within a sentence. It’s like a small pause that helps us make sense of what we’re reading.

Now, you might wonder why we need commas before “which”. I’ll break it down for you. The use of the comma before ‘which’ depends on whether ‘which’ is introducing an essential or nonessential clause.

Let me illustrate this with an example:

  • Essential Clause: The book which I bought yesterday is interesting.

  • Nonessential Clause: The book, which I bought yesterday, is interesting.

In the essential clause, ‘which’ introduces vital information about the book – omitting it would change the meaning of the sentence. Hence no comma is needed before ‘which’. But in the nonessential clause where ‘which’ introduces extra information (the day when I bought), you’ll notice two commas enveloping it – indicating that removing this detail won’t alter our understanding of which book it is.

Simply put, if removing your clause changes your sentence’s meaning then don’t precede ‘which’ with a comma – if not then do!

Still confused? Here’s another set:

  • Essential: Cars which run on diesel are expensive to maintain.

  • Nonessential: My car, which runs on diesel, is expensive to maintain.

The distinction between these two types may seem minute but getting them right can significantly improve your writing’s clarity and precision.

However, remember this rule isn’t set in stone! It largely depends on context and stylistic preference as well. So while adhering to grammar rules can help ensure clear communication, there’s always room for flexibility and personal style!

When to Use a Comma Before ‘Which’: Practical Examples

Let’s dive into the practicalities of using a comma before ‘which’. This seemingly small punctuation mark can significantly impact sentence clarity, and I’ll break down when you should use it — with real-life examples.

Firstly, remember ‘which’ typically introduces non-essential clauses — extra information that doesn’t change the fundamental meaning of the sentence. These clauses are set off with commas. For instance:

“I love my new bookshelf, which I assembled myself.”

Here, even if we remove “which I assembled myself,” the sentence still makes sense: “I love my new bookshelf.”

Contrastingly, when ‘which’ introduces an essential clause (information crucial to understand the sentence), no comma is needed. An example:

“The couch which is in the living room is old.”

Without “which is in the living room,” we wouldn’t know which couch we’re talking about!

Here’s a comparison table to illustrate these points:


Comma before ‘Which’?

“My cat loves his toy mouse, which squeaks.”


“The movie which won best picture was surprising.”


Remember: context and clarity are key! If omitting or including a comma changes your intended meaning or makes your sentence confusing, reconsider your phrasing.

There’s also another important case where you’d use a comma before ‘which.’ In sentences where ‘which’ refers back to an entire clause rather than just one noun, use a comma. For example:

“She forgot her lunch today, which is unusual.”

In this case ‘which’ refers back not just to ‘lunch,’ but rather to the whole action of forgetting her lunch. It’s these little nuances that make English such an exciting language!

To summarize:

  • Use a comma before ‘which’ if it introduces non-essential information.

  • Don’t use a comma if it precedes essential information.

  • Do use a comma if ‘which’ relates back to an entire phrase.

Navigating English grammar might feel like sailing through uncharted waters at times — but with each rule you master, you’re sculpting your linguistic treasure map!

Conclusion: Mastering the Comma Before ‘Which’

By now, I’ve done my best to unpack the mystery of using a comma before “which”. It’s not as daunting as it first seems, right?

Remember that “which” often introduces non-restrictive clauses. These are bits of information that don’t change the meaning of the sentence they’re in. They’re just there to provide additional details. And when you see “which” taking on this role, it’s usually polite to precede it with a comma.

But like most rules in English grammar, there are exceptions. Sometimes you’ll find sentences where “which” begins restrictive clauses – ones that cannot be removed without altering the meaning of the sentence. In these cases, hold back on your instinct to add a comma.

To help remember which is which (pun intended), let’s look at some examples:

Sentence Type


Non-restrictive clause

My car, which is red, needs a wash.

Restrictive clause

The cars which need washing are mine and yours.

In the first example, removing “which is red” doesn’t change the fact that my car needs a wash – so we use a comma before “which”. But in the second sentence if we took out “which need washing”, we’d lose important information about exactly whose cars need washing – no comma necessary!

So there you have it! Mastering commas with “which” really boils down to recognizing whether you’re dealing with restrictive or non-restrictive clauses.

  • Stick with commas before “which” for non-essential info

  • Skip them when “which” introduces essential details

Keep practicing and soon enough, it’ll become second nature!

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