It’s peak summer, and a family is debating what to buy at the store: bug spray to keep the “mosquitoes” away, or is it “mosquitos”? Nobody in the group is entirely sure, and a quick glance at the product label doesn’t help much either, since different brands seem to spell it differently.
This tiny, easily overlooked plural has quietly confused English speakers for generations, and unlike clean-cut British-versus-American spelling pairs like “colour/color,” this one doesn’t split neatly along national lines at all. Both “mosquitos” and “mosquitoes” show up constantly across health warnings, pest control ads, travel advisories, and casual conversation, often within the very same country, sometimes even the very same sentence.
This inconsistency exists because “mosquito” belongs to a notoriously tricky corner of English spelling: nouns ending in “o” that don’t follow one single, universal rule when forming their plural. Some words in this category always add “-es” (like “tomato” becoming “tomatoes”), some always just add “-s” (like “photo” becoming “photos”), and a small, frustrating group — including “mosquito” — technically accepts both forms, depending on which dictionary or style guide you check.
This guide breaks down exactly which spelling is considered the standard, more widely preferred plural, why English handles “-o” endings so inconsistently in the first place, and how to make a confident, defensible choice the next time you’re writing about these persistent, itch-inducing insects.
Quick Answer
Mosquitoes (with “-es”) is the more traditional, widely preferred, and more frequently used plural form of “mosquito” in both American and British English. Mosquitos (with just “-s”) is also considered an acceptable, recognized alternate spelling, though it appears less often in formal, edited writing.
According to Merriam-Webster, both “mosquitoes” and “mosquitos” are listed as valid plural forms, with “mosquitoes” appearing as the primary, more commonly used entry. The Cambridge Dictionary similarly lists “mosquitoes” as the standard plural. When two spellings are both accepted but one is used far more often, style guides and careful writers typically default to the more common, primary form.
A simple way to decide: when in doubt, choose mosquitoes. It’s the safer, more widely recognized choice across news writing, scientific literature, and everyday publishing, while “mosquitos” remains understandable but slightly less standard.
Correct Example
- The lake is swarming with mosquitoes this time of year.
- Health officials warned residents about disease-carrying mosquitoes.
- We sprayed the yard to keep the mosquitoes away before the barbecue.
Also Acceptable (Alternate Spelling)
- The lake is swarming with mosquitos this time of year.
- Health officials warned residents about disease-carrying mosquitos.
Less Common / Avoid in Formal Writing
- The mosquito’s habitat includes both mosquitoe and mosquito forms interchangeably without consistency within a single document. (Inconsistent usage within the same piece should always be avoided, regardless of which spelling you choose.)
What Does Mosquitoes Mean?
Mosquitoes is the plural form of “mosquito,” referring to more than one of the small, flying insects known for biting and feeding on blood, and for their role in spreading various diseases.
Common Meanings
- Insect Plural — more than one mosquito, the flying insect.
- Public Health Context — used in discussions of disease transmission and vector control.
- Pest Control Context — used in marketing and instructions for repellents and traps.
- Everyday Reference — the common way to describe swarms or groups of the insect in casual speech.
Simple Usage Examples
- Health: “Mosquitoes are known to transmit diseases like malaria and dengue fever.”
- Travel: “Pack insect repellent, since mosquitoes are common near the wetlands.”
- Everyday speech: “The mosquitoes were unbearable at the campsite last night.”
- Science: “Researchers study how mosquitoes locate their hosts using scent and heat.”
What Does Mosquitos Mean?
Mosquitos carries the exact same meaning as “mosquitoes,” referring to the plural of the insect, differing only in spelling. It’s an accepted alternate form, though used less frequently in edited, formal writing.
Common Meanings
- Insect Plural (Alternate Spelling) — identical in meaning to “mosquitoes.”
- Informal or Brand Usage — sometimes appears in product names, casual writing, or regional preference.
- Simplified Spelling — reflects the general English tendency to sometimes drop the “-es” ending in favor of a simpler “-s.”
Simple Usage Examples
- Casual writing: “There were so many mosquitos by the pond this evening.”
- Product marketing: “This spray kills mosquitos on contact.”
- Everyday speech: “I hate how loud mosquitos sound near your ear at night.”
Mosquitoes vs. Mosquitos: Comparison Table
| Spelling | Frequency of Use | Formal Writing Recommendation | Dictionary Status |
|---|---|---|---|
| Mosquitoes | More common | Preferred | Primary listed form |
| Mosquitos | Less common | Acceptable, but secondary | Valid alternate form |
Where Each Spelling Tends to Appear
| Context | Common Spelling |
|---|---|
| News and journalism | Mosquitoes |
| Scientific/medical writing | Mosquitoes |
| Casual conversation and social media | Both used interchangeably |
| Product branding/marketing | Mosquitos sometimes used for simplicity |
| Academic and public health documents | Mosquitoes |
The “-O Ending” Plural Rule (and Why It’s So Inconsistent)
English nouns ending in “o” are famous for having no single, reliable pluralization rule, and “mosquito” sits right in the middle of this inconsistency.
Words That Always Add “-es”
| Singular | Plural |
|---|---|
| Tomato | Tomatoes |
| Potato | Potatoes |
| Volcano | Volcanoes (also accepted: volcanos) |
| Hero | Heroes |
Words That Always Just Add “-s”
| Singular | Plural |
|---|---|
| Photo | Photos |
| Piano | Pianos |
| Halo | Halos |
| Solo | Solos |
Words That Accept Both Forms
| Singular | Accepted Plurals |
|---|---|
| Mosquito | Mosquitoes / Mosquitos |
| Volcano | Volcanoes / Volcanos |
| Zero | Zeroes / Zeros |
| Cargo | Cargoes / Cargos |
“Mosquito” falls squarely into this last, most confusing category, which is exactly why so many people search for clarification on which form to use.
The Origin of Mosquito, Mosquitoes, and Mosquitos
Word History
“Mosquito” entered English from Spanish and Portuguese, where it literally means “little fly,” formed from mosca (fly) plus the diminutive suffix -ito (little). Because the word arrived as a loanword from Spanish rather than developing natively within English, its plural form never fully settled into one of English’s more predictable patterns, leaving both the “-es” and “-s” endings to coexist as acceptable options over the centuries.
Why Both Plurals Persist Today
Many loanwords ending in “o,” especially those borrowed from Spanish and Italian, ended up in this same flexible category, since English speakers historically applied inconsistent pluralization habits to foreign-origin words. Over time, “mosquitoes” became the more dominant, standardized form in edited publishing, largely through convention and repeated use in dictionaries, style guides, and journalism, while “mosquitos” remained a recognized, if slightly less common, alternative that never fully disappeared from everyday use.
The “When in Doubt” Rule
A simple way to decide which spelling to use: when you’re uncertain, default to mosquitoes, since it’s the more universally recognized, dictionary-preferred, and stylistically safer choice across nearly all forms of writing. Reserve “mosquitos” only for situations where you’re intentionally matching an established brand name, a specific regional preference, or informal writing where either spelling would be understood without issue.
Which Spelling Should You Use?
News, Journalism, and Publishing
Writers producing news articles, blog posts, or any professionally edited content should default to “mosquitoes,” matching the standard preferred by AP style and most major dictionaries.
Scientific and Medical Writing
Public health organizations, medical journals, and entomology researchers consistently use “mosquitoes” in official documentation and published research.
Marketing and Branding
Pest control companies and repellent brands sometimes use “mosquitos” for stylistic or branding reasons, though this remains a matter of preference rather than a grammatical requirement.
Casual and Conversational Writing
In texts, social media posts, or informal writing, either spelling is easily understood, though “mosquitoes” still remains the more broadly recognized default even in casual contexts.
Academic Writing
Students and researchers should use “mosquitoes” consistently throughout academic papers, matching the standard expected by most style guides and instructors.
Common Mistakes with Mosquitoes and Mosquitos
Frequent Errors
- Mixing both spellings within the same document or article.
- Assuming “mosquitos” is incorrect, when it’s actually a recognized, valid alternate spelling.
- Applying the wrong “-o” plural pattern from a different word, such as assuming mosquito behaves like “photo” (photos) rather than “tomato” (tomatoes).
- Overcorrecting casual writing by treating “mosquitos” as a spelling error rather than an accepted variant.
Corrected Examples
- Incorrect (inconsistent): “The mosquitoes near the pond were worse than the mosquitos near the house.”
- Correct (consistent): “The mosquitoes near the pond were worse than the mosquitoes near the house.”
Mosquitoes and Mosquitos in Everyday Examples
Emails
“Please remember to apply insect repellent, as mosquitoes are especially active during the evening hours at the campsite.”
Social Media
“These mosquitos are eating me alive tonight, someone send bug spray.”
News Writing
“Health officials confirmed an increase in mosquitoes carrying West Nile virus this summer.”
School Writing
“The science project examines how mosquitoes are attracted to certain scents and body temperatures.”
Business Writing
“Our new outdoor spray provides up to eight hours of protection against mosquitoes and other biting insects.”
Why This Keyword Gets Searched
People search “mosquitos vs mosquitoes” mostly while writing something casually and pausing to double-check which spelling looks more correct, especially during summer months when the topic comes up frequently in travel warnings, pest control advertising, and public health messaging. Writers and editors search it while trying to match a specific style guide’s preferred spelling. A smaller group searches it out of general curiosity after noticing both spellings used inconsistently across different websites, packaging, or news sources.
Related Grammar Rules
Similar “-O Ending” Plural Confusions
- Volcano vs. Volcanoes vs. Volcanos — a nearly identical dual-plural situation.
- Tornado vs. Tornadoes vs. Tornados — another commonly confused “-o” ending word.
- Cargo vs. Cargoes vs. Cargos — a comparable flexible plural pair.
Helpful Grammar Tips
Whenever a noun ending in “o” doesn’t clearly fall into a predictable pattern, check a current dictionary for the preferred form, and default to the “-es” ending when both options are listed as acceptable, since it tends to be the more broadly recognized and formally preferred choice across this particular category of English nouns.
FAQs
Is “mosquitos” a real word?
Yes, “mosquitos” is a recognized, valid alternate plural spelling of “mosquito,” though “mosquitoes” is more commonly used and generally preferred.
What is the correct plural of mosquito?
Both “mosquitoes” and “mosquitos” are considered correct, but “mosquitoes” is the more widely used and dictionary-preferred form.
Why do some words ending in “o” add “-es” and others just “-s”?
English inherited these words from different source languages and adopted inconsistent pluralization habits over time, resulting in no single universal rule for words ending in “o.”
Is “mosquitoes” the only correct spelling?
No, “mosquitos” is also accepted, though “mosquitoes” remains the more standard and frequently used choice in formal and edited writing.
Do dictionaries accept both spellings?
Yes, major dictionaries like Merriam-Webster and Cambridge list both “mosquitoes” and “mosquitos” as valid plural forms, with “mosquitoes” typically listed first as the primary entry.
What other words follow the same “-o” plural pattern?
Words like “volcano/volcanoes/volcanos,” “tornado/tornadoes/tornados,” and “cargo/cargoes/cargos” follow the same flexible dual-plural pattern as “mosquito.”
Does AP style prefer “mosquitoes” or “mosquitos”?
AP style, like most major style guides, generally prefers “mosquitoes” as the standard plural form in professional journalism.
Can I use “mosquitos” in formal writing?
While technically accepted, it’s safer to use “mosquitoes” in formal, academic, or professional writing, since it’s the more universally recognized and expected form.
Conclusion
Unlike many of the word pairs covered elsewhere in this series, “mosquitoes” and “mosquitos” don’t split neatly along regional lines or grammatical categories — they simply represent one of English’s genuinely inconsistent corners, where nouns ending in “o” never settled on a single, universal pluralization rule.
“Mosquitoes,” with its traditional “-es” ending, remains the more dominant, dictionary-preferred, and widely recognized choice across journalism, science, and formal writing, while “mosquitos” persists as a valid, understandable alternative that shows up more often in casual writing, branding, and everyday conversation.
Rather than treating this as a strict right-versus-wrong situation, it helps to think of “mosquitoes vs mosquitos” the way you might think of “volcano/volcanoes” or “tornado/tornadoes” — a small, quirky category of English words that simply never resolved into one tidy rule.
When you’re unsure which spelling to reach for, defaulting to “mosquitoes” will serve you well in nearly every formal or professional context, while knowing that “mosquitos” isn’t technically wrong gives you the flexibility to relax about it in casual writing. Either way, the next time these small, persistent insects show up in your writing, you’ll know exactly which spelling carries the stronger claim to being the standard.
Read More Blogs:
- Blame or Blaim? The Best Way to Spell It Right
- Rationale or Rational? The Best Way to Spell It Right
Hi, I am Anne Seaton. I am a writer and educator working with Wordssensei.com to help students learn English easily.
