The construction "or which is" trips up business writers more than you'd expect. It appears in sentences like "Submit the form, or which is easier, call us directly" and "Choose the shorter route, or which is faster, take the bypass." Both feel almost right. Both are almost wrong. Understanding when "or which is" works, when it doesn't, and what to write instead will sharpen every document you produce.
What "or which is" actually does
"Or which is" introduces an alternative description or an alternative option within a sentence. It functions as a connective relative clause, bridging two ideas that the writer wants to present as interchangeable or supplementary. The problem is that this construction is rarely the clearest choice, and in professional writing, clarity beats cleverness every time.
Compare these two sentences:
- Send the completed form by Friday, or which is acceptable, email a scanned copy.
- Send the completed form by Friday. Alternatively, email a scanned copy.
The second version cuts six words and removes all ambiguity. That's the test worth running on every "or which is" you write: can a period and a new sentence do the job better? It usually can.
When "or which is" is grammatically valid
The construction is technically correct when it introduces a relative clause that modifies a noun and offers an equivalent or clarifying alternative. The key requirement is that "which" must refer to a specific noun in the sentence, not a vague idea.
Valid: "We recommend the express courier, or which is equally reliable, the priority postal service."
Here "which" refers back to "the express courier" and the phrase functions as a parenthetical alternative. It's grammatical. It still reads awkwardly in a business context, though, because formal prose expects a tighter structure. Most style guides, including The Chicago Manual of Style, favor restating the noun or restructuring the sentence over stringing relative clauses together with "or."
The "or which is" trap in business emails
Business emails are the most common place to see "or which is" used incorrectly. It usually appears as a filler phrase when the writer is trying to soften a suggestion or offer flexibility without committing to a clean sentence structure. The result is a sentence that feels hesitant and muddy.
Wrong: "Please complete the attached questionnaire, or which is also fine, leave any sections blank that don't apply."
The phrase "or which is also fine" has no noun to attach "which" to. It's floating. The sentence should read: "Complete the attached questionnaire. Leave any sections blank that don't apply."
This pattern shows up alongside other vague connectors. If you find yourself reaching for "or which is" as a bridge between two ideas, stop and ask whether a colon, a period, or a plain "or" would do the work more directly. Nine times out of ten, it will.
"Which" vs "that": the distinction that matters more
Before worrying about "or which is," get the simpler "which" vs "that" decision right. It comes up far more often and has a clear rule.
Use that for restrictive clauses: clauses that define which specific thing you mean. "Send the report that includes the Q2 data." Remove the clause and the sentence loses essential meaning.
Use which for non-restrictive clauses: clauses that add information without changing the sentence's core meaning. "Send the Q2 report, which includes the financial summary." Remove the clause and the sentence still identifies the report correctly.
Non-restrictive "which" clauses always take a comma. Restrictive "that" clauses never do. Get that pairing right and most relative-clause problems disappear before "or which is" even enters the picture. For further guidance on how punctuation shapes clause meaning, the rules around using commas with introductory clauses and phrases follow the same underlying logic.
Four cleaner alternatives to "or which is"
Rather than memorizing when "or which is" is technically permissible, replace it with one of these four constructions every time:
- A new sentence. "Submit the form by Friday. Alternatively, email a scan." Clean, direct, professional.
- A plain "or." "Submit the form or email a scan by Friday." Shorter by half.
- A colon. "You have two options: submit the form or email a scan." The colon signals the list is coming and sets reader expectations correctly.
- Parentheses. "Submit the form by Friday (or email a scan if that's easier)." The parenthetical works when the alternative is genuinely secondary.
Pick whichever fits the rhythm of the surrounding paragraph. Don't default to the longest construction just because it sounds formal.
A note on spoken vs written English
"Or which is" survives in speech because listeners fill gaps in real time. On the page, readers expect every clause to anchor clearly to a noun. The spoken version of "or which is easier, just call us" becomes, in writing, "Alternatively, call us." That's not dumbing down the language. That's understanding what the medium requires.
Business writing rewards directness. Every word that earns its place gets to stay. "Or which is" rarely earns its place. Cut it, restructure the sentence, and move on.