once which

USAGE SUMMARY

The phrase "once which" is not correct and usable in written English.
It is not a standard construction and does not convey a clear meaning in English. Example: "There was a time once which I thought I could fly."

⚠ May contain grammatical issues

News & Media

Science

Human-verified examples from authoritative sources

Exact Expressions

59 human-written examples

"You can strike once, which we did.

The New Yorker

Or both at once, which is more his style.

The New York Times - Books

"We had a ferret once, which was interesting," smiles Walker.

Independent

I only stab myself once, which feels like a triumph.

The Guardian - Lifestyle

Even spilled it once, which is not supposed to happen.

The Guardian - Sport

"And I'm always — actually, I asked her for advice once, which was just really ridiculous.

The New York Times

These conditions seem to be pursuing two objectives at once, which is rarely a sensible idea.

The Economist

You are doing two things at once, which is really good for music.

The New York Times

Yet he downplays this point and only mentions it once, which is awkward.

The Economist

A girl shouted it when she saw me out walking once, which was embarrassing.

The Guardian

"We made a boxing movie once, which was really good fun.

The Guardian - Film

Expert writing Tips

Best practice

Avoid using "once which" in formal writing. Opt for grammatically correct alternatives like "once when" or rephrase the sentence for clarity and correctness.

Common error

Many writers incorrectly use "which" after "once" when referring to a specific time or event. "Which" is typically used to introduce nonrestrictive clauses, while "when" is more appropriate for specifying a time. Avoid saying "I went there once which was fun"; instead, say "I went there once, which was fun" or "I went there once when it was fun".

Linguistic Context

The phrase "once which" functions as a relative clause, but it's grammatically incorrect. It attempts to provide additional information about a preceding noun (usually a time or event). As Ludwig AI indicates, this construction is not standard and lacks clear meaning in English.

Expression frequency: Very common

Frequent in

News & Media

68%

Science

24%

Formal & Business

8%

Less common in

Encyclopedias

0%

Wiki

0%

Reference

0%

Ludwig's WRAP-UP

In summary, while the phrase "once which" appears frequently across various sources, including news media and scientific publications, it is considered grammatically incorrect. Ludwig AI clearly identifies it as a non-standard construction. The correct alternative is often to use "once when" or to rephrase the sentence entirely. Therefore, while the phrase is common, particularly in neutral registers, it should be avoided in formal writing to maintain grammatical accuracy and clarity. Remember that alternatives such as "a time when" or restructuring the sentence can help ensure your writing is both clear and correct.

More alternative expressions

Phrases that express similar concepts, ordered by semantic similarity:

once when

Replaces "which" with "when" to specify a time.

a time when

Uses a more formal structure to refer to a specific time.

one instance where

Highlights a specific occurrence or example.

on one occasion which

Adds formality and emphasizes a particular event.

once that

Replaces "which" with "that", which can work in some contexts but is still not ideal.

the time that

Specifies a particular time frame with added clarity.

a situation in which

Reframes the context to focus on a specific scenario.

an occasion when

Similar to "a time when" but emphasizes the event.

previously which

Indicates something that happened at an earlier time.

formerly which

Describes a prior state or condition.

FAQs

How can I correctly use "once" in a sentence that needs a relative pronoun?

Instead of using the grammatically incorrect phrase "once which", use "once when" if you're referring to a time. Alternatively, rephrase the sentence. For example, instead of saying "I saw him once which was surprising", say "I saw him "him once", and that was surprising".

What are some alternatives to the incorrect phrase "once which"?

Common alternatives include "once when", "a time when", or restructuring the sentence to avoid the need for "which" after "once" altogether.

Is it ever correct to use "which" after "once"?

While it appears in some informal contexts, it's generally not considered grammatically correct. Using "once when" or rephrasing will result in clearer and more grammatically sound sentences.

What's the difference between using "once when" and "once which"?

"Once when" is grammatically correct and refers to a specific time or occasion. "Once which" is generally considered incorrect and should be avoided in formal writing. It's better to use "once when" or rephrase the sentence for clarity.