The phrase which in turn often links an effect to what caused it: one event changes something, and that change leads to another result. Punctuating it correctly depends on the sentence around it, not on a fixed rule that always adds commas around the phrase. In most sentences, a comma comes before which when it begins a supplementary relative clause, and no comma is needed after turn unless the clause itself ends there or another part of the sentence calls for one. Before editing, identify what which refers to and decide whether its clause is essential or additional information.
What You’ll Need
- The complete sentence containing which in turn, including the words before and after it.
- A clear idea of what which refers to and what result the clause describes.
- If you are writing for a class, publication, or workplace, the relevant style guide. Conventions can differ, especially in the treatment of restrictive clauses introduced by which.
Step-by-Step
- Find the full clause that starts with which. Do not punctuate the phrase in isolation. In The new schedule reduced delays, which in turn improved service, the clause is which in turn improved service. It tells the reader what followed from the reduction in delays. Seeing the entire clause makes it easier to tell whether it is complete and where it belongs.
- Identify the antecedent. The antecedent is the word, phrase, or idea that which points back to. In the example above, which refers to the fact that the new schedule reduced delays, rather than to the noun delays alone. A useful check is to ask, “What improved service?” The answer should be the reduction in delays. If readers could reasonably attach which to several different things, rewrite the sentence to make the reference clearer.
- Decide whether the clause is supplementary or essential. A supplementary clause adds information that the reader does not need to identify the noun or understand the main point. Set it off with a comma. For example: The bridge reopened on Monday, which in turn eased traffic downtown. The main statement is that the bridge reopened; the effect is extra information. In many American style guides, a supplementary clause is introduced by which and preceded by a comma.
- Use a comma before which when it introduces that supplementary clause. In the example above, the comma marks the start of the added information. Do not add a comma just because the words which in turn appear together. The comma is there because of the relationship between the relative clause and the rest of the sentence. If the clause is essential to identify a particular noun, punctuation and word choice may need to change; see the style-guide note and examples below.
- Do not automatically put a comma after turn. In the straightforward pattern, the words in turn are part of the clause and read smoothly without internal commas: The new rule clarified responsibilities, which in turn reduced confusion. The comma before which opens the supplementary clause. There is no grammatical need for another comma immediately after turn. Avoid treating which in turn as a phrase that must always be enclosed in commas.
- Check whether the relative clause is in the middle of the sentence. A supplementary clause placed between the subject and the rest of the main clause normally needs a comma at both ends. For example: The revised map, which in turn helped visitors find the entrance, was posted online. The first comma opens the clause; the comma after entrance closes it. Notice that this closing comma is not placed after turn. If the clause comes at the end of the sentence, it needs no closing comma before the period: The map helped visitors find the entrance, which in turn reduced questions at the desk.
- Consider whether in turn is parenthetical. Usually it is closely connected to the meaning of the clause, so it does not need commas of its own. If you want to mark it as a noticeable aside, you may set it off: The change, which, in turn, affected staffing, required another review. This punctuation creates a more interrupted rhythm and is often unnecessary. Use it only when the aside-like emphasis is intended and the sentence remains easy to read. Do not add the pair by habit.
- Read the sentence aloud and check the logic. The punctuation should help readers follow the sequence: first one event, then a resulting effect. If the sentence feels overloaded, split it: The schedule reduced delays. This, in turn, improved service. In the second sentence, this points to the preceding idea, and the comma after turn is appropriate because the sentence uses the parenthetical phrase in turn after its subject. A rewrite can be clearer than adding more commas to a long sentence.
Common Mistakes
Putting commas around the phrase every time. A common overcorrection is The delay, which, in turn, caused a cancellation. The commas around in turn are not required merely because the phrase is familiar. In ordinary prose, write The delay, which in turn caused a cancellation, affected the entire schedule. Use the extra commas only if you deliberately want to set off in turn as an interruption.
Leaving out the comma before a supplementary which clause. In a sentence such as The update fixed the error which in turn restored access, readers may struggle to tell where the main statement ends and the added result begins. If the clause is supplementary, write The update fixed the error, which in turn restored access. The comma signals that the following clause adds a consequence rather than identifying which error you mean.
Adding a comma between which and in turn. Do not write which, in turn improved. If in turn is not being set off as a parenthetical, the words should stay together: which in turn improved. If you do choose to mark in turn parenthetically, punctuation must appear on both sides: which, in turn, improved.
Using which when its reference is unclear. A comma cannot fix an ambiguous antecedent. In The team reviewed the report after the manager changed it, which in turn caused delays, which could refer to the report being changed or to the review. Name the cause: The manager’s changes to the report caused delays in the review.
Assuming every which clause is nonessential. Some writers use which for essential clauses, and conventions differ by region and style guide. Many American guides prefer that without a comma for a restrictive clause, as in Choose the route that avoids the closure. Follow the rules expected by your audience, and make sure the punctuation reflects whether the information is essential.
Tips
- Use the remove-it test. Temporarily delete the which clause. If the sentence still identifies the subject or object and keeps its main point, the clause is likely supplementary and should generally be set off with commas. This test is a guide, not a substitute for checking the intended meaning.
- Keep the cause-and-effect chain close. Place which in turn near the result it introduces. If several clauses intervene, readers may lose track of what caused what. Shortening or dividing the sentence often solves the problem.
- Use this in turn to refer to a whole preceding idea. When the result is a consequence of an entire statement, a new sentence can make the reference more direct: The figures were corrected. This, in turn, changed the final total.
- Apply one style consistently. If a style guide distinguishes restrictive that clauses from supplementary which clauses, use that distinction throughout the document. If you are following another variety of English or a publisher’s house style, follow its stated convention.
- Prefer the least punctuation that makes the structure clear. Commas should show clause boundaries or intentional interruptions. They are not decorations around a phrase that sounds like a transition.
Troubleshooting
If you are unsure whether a comma belongs before which: Decide whether the clause supplies extra information or identifies a particular thing. If it is an extra consequence, the supplementary pattern normally takes a comma: The first test failed, which in turn prompted a second test. If it identifies which item you mean, check the style rule for your audience and consider using that in American English where appropriate.
If you cannot tell what which refers to: Replace which with a specific noun or a phrase such as this result. For example, revise The team moved the deadline after the review, which in turn changed the plan to The review led the team to move the deadline, and that change altered the plan. The revision clarifies the sequence instead of asking punctuation to solve a reference problem.
If the sentence seems to need commas everywhere: Mark the main subject and verb first, then bracket only the supplementary clause. For The proposal, which in turn affected the budget, was approved, the main structure is The proposal was approved; the two commas enclose the added clause. Do not add another comma after turn unless you are intentionally setting off in turn as a parenthetical.
If the result sounds like a new thought: End the first sentence and begin the next with This, in turn, … or state the cause directly. This is especially useful when the original sentence has multiple causes, several commas, or a long subject. A clear sentence boundary is better than a technically possible but hard-to-follow chain of clauses.
Frequently Asked Questions
Do you put a comma before which in turn?
Usually, yes, when which introduces a supplementary relative clause: The change reduced waste, which in turn lowered costs. The comma marks the clause boundary, not a special rule for the phrase itself.
Do you put a comma after which in turn?
Not in the usual pattern. Write which in turn lowered costs without a comma after turn. A comma there is appropriate only when it closes a parenthetical phrase or another construction independently requires it.
Should in turn have commas around it?
Usually not. It commonly works as an integrated adverbial phrase: The change, which in turn lowered costs, was retained. You can write which, in turn, lowered costs to emphasize it as an aside, but that punctuation is optional and can make the sentence feel interrupted.
Is which in turn grammatically correct?
Yes, when which has a clear antecedent and the clause fits the sentence. The phrase often expresses a next step or consequence. If the reference is vague, revise the sentence rather than relying on commas to clarify it.
Can I start a sentence with which in turn?
Usually not as a complete sentence on its own, because a relative clause beginning with which normally depends on another clause. You can start a new sentence with This, in turn, … to refer to the preceding idea, or attach the which clause to the sentence it describes.
Should I use that instead of which?
It depends on the clause and the style you are following. Many American guides favor that for essential information and which with a comma for supplementary information. Other conventions allow restrictive which. Make the meaning clear and follow the relevant style guide.