“Passersby” is the only correct plural of “passerby.” “Passerbyers” is not a real word in standard English, and “passerbys” is also wrong. The mix-up happens because “passerby” is a compound noun, and English pluralizes the noun part inside it (“passer”), not the whole word as a single unit.
Quick Answer
| Form | Correct? | Notes |
|---|---|---|
| Passersby | ✅ Yes | The only standard plural |
| Passerbys | ❌ No | Treats the compound as one simple word |
| Passerbyers | ❌ No | Adds “-ers” where it doesn’t belong |
- Correct: Several passersby saw the car swerve off the road.
- Incorrect: Several passerbyers saw the car swerve off the road.
The key difference: “passerby” is built from “passer” (the noun) plus “by” (a direction word). When you make it plural, only “passer” changes.
What Does “Passerby” Mean?
A passerby is someone who happens to be walking or moving past a particular place, often just as something notable happens there. It usually describes an incidental observer rather than someone directly involved in an event.
Word origin: The word comes from combining “passer” (one who passes) with “by” (indicating movement past something). Older English writing hyphenated it as “passer-by,” and that spelling is still used today in some British texts.
Part of speech: “Passerby” is a noun only. It has no verb, adjective, or adverb form of its own.
Example:
- A passerby noticed smoke coming from the second-floor window and called the fire department.
Why “Passerbyers” Is Wrong: The Compound-Noun Pluralization Rule
Most English nouns become plural by adding “-s” or “-es” to the end: one dog, two dogs; one box, two boxes. That pattern is so automatic that writers naturally try to apply it here too, which is exactly how “passerbyers” and “passerbys” happen.
But “passerby” isn’t a simple noun — it’s a compound made of a noun (“passer”) and a preposition (“by”). In compounds like this, English pluralizes the noun element, not the preposition or the compound as a whole. “Passer” becomes “passers,” and “by” stays exactly as it is, giving you “passersby.”
“Passerbyers” adds “-ers” onto a word that already ends in a form of “-er” (“passer”), which effectively double-marks the noun and isn’t a recognized formation in English at all.
Is “Passerbys” Also Incorrect?
Yes. “Passerbys” is a genuine mistake too, though a more understandable one than “passerbyers.” It follows the regular “-s” pattern that works for most English nouns, but “passerby” doesn’t follow that pattern because of its compound structure. Only “passersby” is accepted in dictionaries and standard usage.
How to Pronounce “Passersby”
Say it as PASS-erz-by, with the stress on the first syllable. It has three syllables: pass-ers-by. The “s” in “passers” sounds like a “z,” similar to how it sounds in “cars” or “doors.”
For the singular form, “passerby,” Wiktionary lists the standard US pronunciation as /ˈpæs.ɚˌbaɪ/ and the British Received Pronunciation as /ˈpɑː.sə.baɪ/. The plural follows the same pattern, with an added “-z” sound at the end of “passers.”
Passerby and Passersby in Example Sentences
Sentences Using “Passerby” (Singular)
- A passerby stopped to help the driver change a flat tire.
- The witness statement came from a passerby who happened to be walking her dog nearby.
- On the job application, she described how a passerby’s quick thinking once helped her during an emergency.
Sentences Using “Passersby” (Plural)
- Passersby gathered to watch the street musician’s performance.
- The report noted that several passersby had contacted emergency services before officers arrived.
- In the workplace incident report, three passersby were listed as witnesses to the accident.
Possessive Form: “Passerby’s” and “Passersby’s”
The singular possessive is passerby’s, formed the normal way with an apostrophe and “-s.”
- Example: The passerby’s phone captured the entire incident on video.
The plural possessive is passersby’s, adding an apostrophe and “-s” after the full plural form (not just an apostrophe, since “passersby” doesn’t end in “-s”).
- Example: The passersby’s accounts of the event all matched.
Common Mistakes to Avoid
Adding “-ers” to the End
- Incorrect: The passerbyers called for help.
- Correct: The passersby called for help.
- Explanation: “By” never takes a plural ending, and “passer” already carries the plural marker as “passers.”
Treating “Passerby” as Already Plural
- Incorrect: One passersby saw the whole thing happen.
- Correct: One passerby saw the whole thing happen.
- Explanation: “Passerby” is singular; “passersby” is reserved for more than one person.
Other Compound Nouns That Follow the Same Pattern
“Passersby” isn’t an isolated oddity. A handful of other English compound nouns pluralize their main noun instead of their final word:
- One mother-in-law → two mothers-in-law
- One attorney general → two attorneys general
- One runner-up → two runners-up
- One hanger-on → two hangers-on
In each case, the true noun sits in the middle or at the front of the compound, so that’s the part that gets pluralized.
Passerby vs. Bystander vs. Onlooker: What’s the Difference?
These three words overlap but aren’t identical.
- Passerby: Someone who happens to be walking or traveling past a location, usually by chance and often without stopping.
- Bystander: Someone who is present at an event, especially one involving conflict, danger, or wrongdoing, and who is nearby enough to witness or potentially act.
- Onlooker: Someone who is watching something happen, often out of curiosity, without necessarily being close by chance — they may have stopped specifically to watch.
They’re related but not fully interchangeable. A passerby may become a bystander the moment something happens in front of them, but not every bystander was simply “passing by” — some were already at the scene.
Example:
- A passerby noticed the crowd and stopped, becoming one of several bystanders watching the standoff, while onlookers on the balcony above filmed it all.
Passerby vs. Passer-by: American and British Spelling
American English almost always writes this word as one closed compound: passerby. British English has traditionally preferred the hyphenated form, passer-by, and you’ll still see it in some UK publications and older texts.
The plural doesn’t change based on this spelling choice — both styles use passersby as the plural, without a hyphen, since the hyphenated plural “passers-by” has largely fallen out of common use even in British writing, though it does still appear.
Passerby or Passersby: Quick Rule for Choosing the Right Form
Use this simple check: if you’re talking about one person, use “passerby.” If you’re talking about more than one, use “passersby.” Never use “passerbyers,” and avoid “passerbys.”
Memory trick (a learning aid, not an official grammar rule): Think of “passerby” as secretly “a passer who goes by.” When there’s more than one, you get more “passers” — so it becomes “passersby,” with “by” tagging along unchanged at the end.
Quick Quiz: Test Yourself on Passerby vs. Passersby
- Fill in the blank: A ______ called the police after seeing the break-in. (passerby / passersby)
- Choose the correct sentence: “Two passerby helped push the stalled car.” or “Two passersby helped push the stalled car.”
- Correct the sentence: “The passerbyers watched the parade from the sidewalk.”
- Fill in the blank: The ______ opinion was the only eyewitness account available. (passerby’s / passersby’s)
- Choose the correct word: “Several ______ noticed the smoke before the alarm went off.” (passerbys / passersby)
- True or False: “Passer-by” is an acceptable British spelling of “passerby.”
- Identify the error: “One passersby stopped to ask for directions.”
Answer Key
- passerby — singular subject (“A ______”).
- “Two passersby helped push the stalled car.” — plural subject requires “passersby.”
- Correct version: “The passersby watched the parade from the sidewalk.” “Passerbyers” is not a standard English word.
- passerby’s — referring to one person’s opinion.
- passersby — “passerbys” is an incorrect plural.
- True — “passer-by” is a recognized British spelling, though “passerby” is now more common overall.
- Error: “passersby” should be “passerby,” since “one” indicates a single person.
Frequently Asked Questions
What is the correct plural of “passerby”? The correct plural is “passersby.” It’s formed by pluralizing “passer,” the noun part of the compound, while “by” stays unchanged.
Is “passerbyers” ever acceptable in any context? No. “Passerbyers” is not recognized in standard English in any register, formal or informal, and it doesn’t appear in major dictionaries.
Is “passerbys” the same mistake as “passerbyers”? Both are incorrect, but “passerbys” is the more understandable mistake since it follows the regular “-s” plural pattern. “Passerbyers” adds an ending that doesn’t belong on either part of the compound.
Why doesn’t “passerby” just take an “-s” like most nouns? Because it’s a compound noun made of “passer” and “by,” and English pluralizes the noun component in these compounds rather than treating the whole word as a single unit.
How do you pronounce “passersby”? It’s pronounced PASS-erz-by, with three syllables and stress on the first one. The “s” in “passers” has a “z” sound.
What is the possessive form of “passerby”? The singular possessive is “passerby’s,” as in “the passerby’s account of events.”
What is the possessive form of “passersby”? The plural possessive is “passersby’s,” as in “the passersby’s statements.”
Is “passer-by” (with a hyphen) still correct? Yes, particularly in British English, where the hyphenated form has traditionally been standard. American English generally favors the closed form “passerby.”
Do British and American English spell “passerby” differently? Slightly. American English typically uses “passerby,” while British English has traditionally used “passer-by.” Both use “passersby” as the plural.
What’s the difference between a passerby and a bystander? A passerby is someone moving past a location by chance, while a bystander is someone present at an event, often implying they’re near enough to witness or respond to it. A passerby can become a bystander once something happens in front of them.
Is “passerby” a noun or can it be used as a verb? “Passerby” is a noun only. There is no verb form of the word itself, though it’s related to the verb phrase “to pass by.”
What are some synonyms for “passersby”? Common alternatives include bystanders, onlookers, and pedestrians, though each carries slightly different shades of meaning depending on context.
The Bottom Line
“Passersby” is the only correct plural of “passerby.” Both “passerbyers” and “passerbys” are mistakes that come from applying the regular “-s” plural rule to a word that doesn’t follow it. Remember the compound structure — “passer” plus “by” — and pluralize only the noun part: one passerby, several passersby.
