is cause (caused) by

Writers often type or say "is cause by" when they mean "is caused by." After a form of be you need the past participle (caused), not the base verb (cause). Below are quick rules, fast editing checks, many wrong/right pairs, and easy rewrites for work, school and casual writing.

Quick answer

Use the past participle: is caused by, was caused by, are caused by. "Is cause by" is ungrammatical-change cause → caused, or rewrite in active voice or with "because of."

Correct: The delay is caused by heavy traffic.
Incorrect: The delay is cause by heavy traffic.
Fast fixes: change cause → caused; or rewrite as "Y caused X"; or use "X happened because of Y."

Core explanation: grammar you can scan in one pass

Look for this passive pattern: [subject] + [be (is/are/was/were/has been)] + [past participle] + by + [agent/reason]. For the verb cause, the past participle is caused.

Formula: X is/was/are + caused + by + Y
If you spot "be" + cause (base verb), change cause → caused. If it still sounds awkward, switch to active voice or "because of."
Active alternative: Y caused X. Reason phrase
alternative: X happened because of Y.

Wrong: The page downtime is cause by a bad deploy.
Right: The page downtime is caused by a bad deploy.
Wrong: Production errors were cause by missing tests.
Right: Production errors were caused by missing tests.

Real usage: when to use passive vs active

Use the passive when you want to emphasize the outcome or keep the actor unimportant. Use active to name responsibility or make the sentence direct and concise.

Passive (focus on effect): "The symptoms are caused by exposure to X."
Active (focus on actor): "Vendor errors caused the delays."
Short, casual messages often prefer "because of" or the active form for clarity.

Scientific: The defects are caused by corrosion of the alloy.
Report: Customer complaints were caused by a billing error.
Direct: A configuration mistake caused the outage.

Examples

Work - common email/report lines (wrong → right)

Wrong: The shipment delay is cause by customs clearance.
Right: The shipment delay is caused by customs clearance.
Wrong: Backup failures are cause by expired certificates.
Right: Backup failures are caused by expired certificates.
Wrong: Q1 revenue miss is cause by forecast errors.
Right: Q1 revenue miss was caused by forecast errors.
Wrong: The security breach is cause by an unpatched server.
Right: The security breach was caused by an unpatched server.

School - essays, lab reports and feedback

Wrong: The experiment failure is cause by contaminated reagents.
Right: The experiment failure was caused by contaminated reagents.
Wrong: Low turnout is cause by poor advertising.
Right: Low turnout was caused by poor advertising.
Wrong: The species loss is cause by habitat fragmentation.
Right: The species loss is caused by habitat fragmentation.
Wrong: The grade drop is cause by missed assignments.
Right: The grade drop was caused by missed assignments.

Casual - texts, notes, social posts

Wrong: My phone is cause by water damage.
Right: My phone is damaged - it was caused by water.
Wrong: The party is cause by the rain.
Right: The party was canceled because of the rain.
Wrong: This mess is cause by the dog.
Right: This mess was caused by the dog.
Wrong: We're late is cause by traffic.
Right: We're late because of traffic.

Try your own sentence

Test the full sentence, not just the phrase. Context usually clarifies whether passive or active works better.

Rewrite help: quick patterns and copy/paste fixes

Use one of three repairs right away: (A) fix the verb (cause → caused), (B) switch to active voice, or (C) swap in "because of." Templates and direct rewrites below make edits fast.

Templates: "X is/was caused by Y." | "Y caused X." | "X happened because of Y."
Pro tip: find "is cause" / "are cause" and replace with "is caused" / "are caused," then review for tone.

Rewrite:
Wrong: "The outage is cause by a server error." → Fix A: "The outage was caused by a server error."
Rewrite:
Wrong: "Project delays are cause by poor planning." → Fix B: "Poor planning caused the project delays."
Rewrite:
Wrong: "Grades are cause by incomplete homework." → Fix C: "Grades dropped because of incomplete homework."
Rewrite:
Wrong: "Delivery issues are cause by the courier." → Fix A: "Delivery issues are caused by the courier."
Rewrite:
Wrong: "The error is cause by my typo." → Fix B: "My typo caused the error."
Rewrite:
Wrong: "Meeting canceled is cause by illness." → Fix C: "The meeting was canceled because of illness."

Memory tricks and fast edit checks

Two quick scans stop the error almost every time:

Scan for a form of be (is/are/was) - if you find one, expect a past participle next; change cause → caused.
Read the sentence as "Y caused X" - if that sounds natural, prefer the active form.

Mnemonic: Be + Past (Be + d) - when you see be, add -d if the verb is "cause" (cause → caused).
Edit test: search for "is cause", "are cause", "was cause" - those are almost always wrong.
Speed swap: if unsure, replace "is cause by" with "is caused by" and re-read; if it feels wordy, use active or "because of."

Hyphenation and spacing: formatting can hide the error

Hyphenation or line breaks can separate the final d or split the phrase so proofreading misses the missing -d. Keep the verb together and normalize spacing so the eye catches the error.

Don't split "caused" across lines (avoid "cause-" at line end).
In tight layouts, keep "is caused by" on one line when possible so it's easy to spot.

Wrong: Bad break: "The outage is cause- by a surge."
Right:
Fixed: "The outage is caused by a surge."

Mini grammar cheatsheet

Common passive forms with cause: is caused by, are caused by, was caused by, were caused by, has been caused by, have been caused by. Also watch related constructions:

"cause to" (needs an object): "They caused the delay."
Adjectives: "causal" (relating to cause) or "caused" used adjectivally.
Never use "caused of" - use "caused by" or "because of."

Correct passive: "The glitch was caused by a typo."
Correct active: "A typo caused the glitch."
Incorrect: "The flood was caused of heavy rain." →
Correct: "The flood was caused by heavy rain."

Similar mistakes to watch for

Writers who slip with "is cause by" often confuse prepositions, participles, or verb placement. Quick fixes:

Wrong preposition: "caused of" → Correct: "caused by" or "because of."
Missing participle in other verbs: "was affect by" → "was affected by."
Misplaced "to": "They caused to delay the project." → "They caused the project delay."

Wrong: "She was affect by the news." →
Right: "She was affected by the news."
Wrong: "The change caused of schedule shifts." →
Right: "The change was caused by schedule shifts."

FAQ

Is "is caused by" passive voice?

Yes. It uses a form of be + past participle and names the effect (X) and the reason/agent (Y).

Can I ever say "is cause by"?

No. "Is cause by" combines an auxiliary with a base verb and is ungrammatical. Change cause → caused or rewrite the sentence.

When should I choose active voice instead?

Choose active when you want to name the actor or make writing direct: instead of "Delays are caused by the vendor," say "The vendor caused the delays."

Is "because of" interchangeable with "caused by"?

Both express cause, but "caused by" fits passive constructions with a verb, while "because of" introduces a reason phrase. Pick the one that matches your sentence structure and tone.

Quick trick to find all mistakes in a document?

Search for "is cause", "are cause", "was cause", then change to "is caused", "are caused", "was caused" and review each sentence for clarity.

Want a fast sentence check?

Paste a sentence into a grammar tool or ask a colleague to glance at it. Try the three quick fixes-add -d, switch to active, or use "because of"-and you'll stop this slip from recurring.