A which synonym is rarely a single word, because which does grammar work rather than carrying meaning. The usual swaps are that, what, which one and whichever, and sometimes the cleanest fix is to break a long sentence in half.
Writers go looking for another word for which when an essay paragraph has six of them stacked up. Below you will see the five jobs which does, the safe replacement for each and the comma rule that decides between which and that.
Swatch at a glance
Best swaps
that, what, which one, whicheverPart of speech
Relative pronoun, question word, determinerMost formal
a fact that, wherebyMost casual
what, which oneAntonyms
None. Which is a grammar word with no opposite.Watch out
Do not use which for people. Write "the nurse who helped me," not "the nurse which helped me."Related forms
whichever, of which, in which, by which
Five jobs, five swaps
| Job | Replace with | Sample |
|---|---|---|
| Question about a set | what, which one | Which bus goes downtown? What bus goes downtown? |
| Defining clause | that | The jar that has a red lid is mine. |
| Extra detail | and it, and this | I bought a lamp, and it was cheap. |
| Comment on a whole idea | and this, a fact that | He missed the train, and this made him late. |
| Any of several | whichever, any | Take whichever seat you like. |
Pick the job first. A swap that fits a question will break a relative clause.
The which synonym that matters most: that
In American English, that introduces a clause that narrows down which thing you mean, with no commas. Which adds bonus detail, set off by commas.
- The report that I sent on Monday has errors. (One report out of several.)
- The report, which I sent on Monday, has errors. (There is only one report.)
British writers often use which in both cases, so you will see "the report which I sent." Either way, never drop the commas around a which clause that only adds detail.
Which or what in a question
Which asks about a small, known set. What is open ended. A waiter with three soups asks "which soup would you like," while a friend with no menu asks "what do you want to eat." In casual speech people swap them freely, but in careful writing the difference reads well.
Which one is the most natural spoken form: "Which one is yours?" For plural sets, use which ones.
Rewrites when which piles up
- The plan, which was approved, which pleased staff becomes staff were pleased that the plan was approved.
- Prices rose, which hurt sales becomes prices rose and sales fell.
- The tool which we use daily becomes the tool we use daily (just drop the word).
- A method by which costs drop becomes a method that cuts costs.
- Rain fell all week, which meant the match was canceled becomes rain fell all week, so the match was canceled.
A student essay line: "Sea levels are rising, which is caused by melting ice, which is linked to warming." Revised: "Melting ice, linked to warming, is raising sea levels." One clause does the work of three.
Linking words such as so and therefore often replace a which that really means a result.
Formal phrases: in which, of which, whereby
In academic writing, in which can often become where: "a town in which crime fell" becomes "a town where crime fell." Whereby means by which and suits legal or policy prose, but it can feel stiff. Of which can often become whose: "a house whose roof leaks."
The transition and linking words section collects more of these connectors.
Common mistakes with which
Using which for a person is the most frequent slip; use who or that. Another is a dangling which with no clear noun: "He forgot the tickets and the snacks, which upset everyone." Was it the tickets, the snacks or the forgetting? Name it: "Forgetting the tickets upset everyone."
Finally, whichever and whatever are not the same. Whichever picks from a known set, while whatever is open.
Frequently asked questions
Can I always use that instead of which?
Only in defining clauses with no commas. After a comma, that is not allowed: the car, that is red is wrong. Use which there.
What can replace which at the start of a question?
What works in most questions, and which one sounds natural in speech. Use which when the choices are limited and known.
How do I avoid starting a sentence with which?
Replace a sentence opening which with this or that: This shows the plan worked. Starting with which is fine only in questions.
Is whereby a good substitute in essays?
It works in formal or legal writing for by which. In most essays, through which or a simple rewrite with that sounds more natural.
Does which have an antonym?
No. Which is a function word that points to something, so it has no opposite in meaning.