When choosing between flys and flies, the correct spelling depends on the word form. In standard English, flies follows established English spelling rules for both a plural noun and a third-person singular present-tense verb. So, flys is generally a spelling error in modern English and ordinary usage. Understanding this spelling pattern helps English learners avoid a common grammar mistake.
For example, flies can describe a winged insect, as in flies in the kitchen, or show an action, as in he flies a plane. The key rule involves verbs ending in -y and certain nouns, where y to ies rule applies. This guide explains the plural of fly, fly as a noun, fly as a verb, and the correct verb form. It also provides clear example sentences for accurate writing.
Quick Answer
Flies is the correct standard spelling. Flys is not the normal English plural or verb form of fly.
There are two especially common situations:
- Flies as a plural noun: “Several flies were buzzing around the room.”
- Flies as a verb: “The eagle flies over the mountains.”
The spelling changes from y to ie because fly ends in a consonant followed by y. English commonly changes that y to i before adding -es when forming certain plurals.
The same pattern appears in words such as:
- baby → babies
- city → cities
- story → stories
- try → tries
- carry → carries
- study → studies
Cambridge’s grammar guidance gives the same general plural pattern for nouns ending in a consonant plus y.
So if you’re choosing between flys or flies, choose flies in standard English.
Comparison Overview
| Form | Correct? | Main use | Example |
| flies | Yes | Plural noun | “The flies gathered near the window.” |
| flies | Yes | Third-person singular verb | “The bird flies south.” |
| fly | Yes | Singular noun or base verb | “I saw a fly.” / “Birds fly.” |
| flew | Yes | Past tense of fly | “The plane flew over the city.” |
| flown | Yes | Past participle | “The birds have flown away.” |
| flying | Yes | Present participle or gerund | “The birds are flying.” |
| flys | No, in standard usage | Not the standard plural or verb form | Avoid “Two flys…” |
Oxford identifies flies as the plural of fly. Its American English dictionary does the same. Cambridge also lists flies as the plural form.
That gives you a simple rule to remember:
Fly becomes flies when you need the standard plural noun or third-person singular present-tense verb.
Main Differences Between Flys and Flies
The biggest difference is simple: flies is standard English while flys isn’t the standard spelling for these grammatical forms.
However, understanding why helps you remember it rather than simply memorizing it.
“Flies” as a plural noun
When you’re talking about more than one insect called a fly, use flies.
For example:
- “A fly landed on the table.”
- “Two flies landed on the table.”
- “The flies disappeared when we opened the window.”
- “Fruit flies can become a nuisance in kitchens.”
- “Several flies were buzzing around the trash.”
Oxford defines a fly as a small flying insect with two wings and gives flies as its plural.
The spelling follows a familiar English pattern:
fly → flies
Not:
fly → flys
The same change occurs in many nouns that end with a consonant followed by y.
“Flies” as a verb
Flies also works as a verb. In this case, it means that one third-person subject performs the action of flying.
Consider these examples:
- “The bird flies over the lake.”
- “The plane flies to Boston every morning.”
- “A butterfly flies from flower to flower.”
- “The eagle flies above the valley.”
- “She flies home every December.”
The subject matters here.
| Subject | Correct form |
| I | fly |
| You | fly |
| We | fly |
| They | fly |
| He | flies |
| She | flies |
| It | flies |
English generally marks the third-person singular present tense with -s. Cambridge’s grammar guidance explains that regular verbs use an -s ending with third-person singular subjects such as he, she, and it.
Because fly already ends in consonant + y, the spelling changes as part of that form:
fly → flies
So you write:
“He flies every weekend.”
You don’t write:
“He flys every weekend.”
Why Does Fly Become Flies?
The answer lies in a common English spelling rule.
When a noun ends in a consonant + y, English usually changes the y to i and adds -es to create the plural.
For example:
| Singular | Plural |
| baby | babies |
| city | cities |
| country | countries |
| family | families |
| story | stories |
| fly | flies |
Cambridge describes this rule directly: nouns ending in a consonant plus y generally change the y to i before adding -es.
There’s an important detail, though.
Not every word ending in y follows this exact pattern.
If a word ends in a vowel + y, English usually keeps the y and simply adds s.
Compare:
| Singular | Plural |
| fly | flies |
| baby | babies |
| city | cities |
| story | stories |
| boy | boys |
| toy | toys |
| day | days |
| key | keys |
Why the difference?
Look at the letter immediately before y:
- fly → the l is a consonant → flies
- baby → the b is a consonant → babies
- boy → the o is a vowel → boys
- toy → the o is a vowel → toys
This small spelling distinction explains a surprising number of English mistakes.
Read More: Traveled or Travelled: Which Spelling Is Correct?
Flys or Flies in Everyday Sentences
Seeing the words inside real sentences makes the difference easier to recognize.
Correct use of “flies” as a noun
When you’re talking about several insects, flies is the plural.
Examples include:
- “The flies kept landing on the fruit.”
- “We noticed several flies near the garbage bin.”
- “The kitchen window was covered with flies.”
- “Fruit flies appeared after the bananas became overripe.”
- “The farmer tried to keep flies away from the animals.”
Here, flies answers the question “How many?”
One insect is a fly.
More than one is flies.
Correct use of “flies” as a verb
When one person, animal, or thing performs the action, flies can function as the verb.
Examples:
- “The hawk flies high above the trees.”
- “She flies to Denver twice a month.”
- “The plane flies across the Atlantic.”
- “The butterfly flies toward the garden.”
- “The kite flies well in strong wind.”
In these sentences, flies describes an action.
That distinction gives you a useful shortcut:
If you’re talking about several insects, flies is a plural noun. If you’re describing what one third-person subject does, flies is a verb.
Common Mistakes With “Flys or Flies”
The mistake usually happens because English learners notice that many plural nouns simply take -s.
For example:
- car → cars
- book → books
- house → houses
- bird → birds
It’s tempting to apply the same pattern mechanically:
fly + s = flys
But English spelling doesn’t work that way here.
The standard form changes the y:
fly → flies
Mistake 1: Using “flys” for multiple insects
Incorrect:
“There were five flys in the room.”
Correct:
“There were five flies in the room.”
The noun needs its standard plural form.
Mistake 2: Using “flys” after he, she, or it
Incorrect:
“The bird flys over the house.”
Correct:
“The bird flies over the house.”
The verb needs its third-person singular present form.
Mistake 3: Confusing “flies” with “flew”
These words belong to different grammatical forms.
- flies = present tense, third-person singular
- flew = past tense
- flown = past participle
For example:
“The animal flies over the lake every morning.”
“The bird flew over the lake yesterday.”
“The bird has flown over the lake several times.”
Oxford identifies flew as the past tense of fly.
Mistake 4: Confusing “flies” with “flying”
Flying is the -ing form.
Compare:
- “The bird flies every morning.”
- “The bird is flying right now.”
The first sentence describes a habitual or general action.
The second describes an action happening around the current moment.
Fly, Flies, Flew, Flown, and Flying Explained
The word fly has several important grammatical forms. Learning them together makes the whole family easier to remember.
| Form | Grammatical role | Example |
| fly | Base verb | “Birds fly south.” |
| flies | Third-person singular present | “The bird flies south.” |
| flew | Simple past | “The bird flew south.” |
| flown | Past participle | “The bird has flown south.” |
| flying | Present participle / gerund | “The bird is flying south.” |
Notice how flies sits between the base form and the past forms.
The pattern isn’t:
fly → flys → flyed
English uses an irregular verb pattern instead:
fly → flies → flew → flown → flying
That’s why memorizing the complete family can help more than memorizing one spelling in isolation.
A Closer Look at “Fly” as a Noun
The noun fly doesn’t always refer to exactly the same thing.
The most familiar meaning describes an insect. Oxford defines it as a small flying insect with two wings.
For example:
“A fly landed on the window.”
The plural is:
“Several flies landed on the window.”
The word also appears in specific fields and expressions.
Fly fishing
In fishing terminology, a fly can refer to an artificial lure designed to resemble an insect or another small food source. Oxford includes this sense in its dictionary entry for fly.
The plural remains flies when you’re talking about multiple artificial flies.
The fly of trousers
There’s another established meaning that can surprise American readers.
In British English, fly can refer to the opening at the front of a pair of trousers. Oxford notes that British English also uses flies in the plural for this sense. Cambridge similarly records flies as a British English plural relating to trousers.
American English more commonly uses fly as the singular noun for this part of pants.
For example:
“His fly was open.”
This meaning doesn’t change the answer to the spelling question. The standard spelling remains fly for singular and flies where the plural form applies.
Flies in Theater Terminology
English has another specialized use of flies.
In theater, the flies refers to the space above the stage where scenery, lighting equipment, and other stage materials may be stored or operated.
Oxford records this as a separate meaning of the flies.
For example:
“The crew moved the scenery into the flies.”
This meaning has nothing to do with insects. Context tells you which meaning applies.
That’s one reason English vocabulary can feel slippery. A single spelling can carry several meanings depending on the sentence around it.
British English vs. American English: Is “Flys” Different?
No.
You might occasionally encounter claims that flys belongs to one variety of English while flies belongs to another. Standard dictionaries don’t support that as a general spelling distinction.
For the ordinary plural of the insect, both American and British English use flies. Oxford’s American English entry explicitly gives flies as the plural of fly.
Cambridge likewise lists flies as the plural.
There are regional differences involving meanings rather than the basic spelling:
| Usage | American English | British English |
| More than one insect | flies | flies |
| He/she/it flies | flies | flies |
| Trousers/pants opening | fly | fly or flies depending on construction |
| Theater space above stage | the flies | the flies |
So don’t treat flys as an American-versus-British spelling choice. It isn’t the standard alternative.
Why “Flys” Looks Plausible
There’s a good reason this mistake feels natural.
English has many words that form plurals simply by adding s:
- table → tables
- chair → chairs
- tree → trees
- phone → phones
- window → windows
A reader may therefore see fly and instinctively add s.
The problem appears when the word ends in consonant + y.
English spelling often changes that ending:
- fly → flies
- cry → cries
- try → tries
- reply → replies
- supply → supplies
The pattern becomes easier once you stop thinking of the plural as “add an s” and instead recognize it as a spelling transformation.
“Flies” vs. Similar Words Ending in Y
A useful comparison can prevent future mistakes.
| Word | Correct third-person form | Correct plural |
| fly | flies | flies |
| try | tries | tries |
| cry | cries | cries |
| carry | carries | carries |
| study | studies | studies |
| play | plays | plays |
| enjoy | enjoys | enjoys |
| buy | buys | buys |
The crucial factor is the letter before y.
Consonant + y
Change y to i and add the appropriate ending.
Examples:
- try → tries
- study → studies
- baby → babies
- fly → flies
Vowel + y
Keep the y and add s.
Examples:
- play → plays
- enjoy → enjoys
- boy → boys
- key → keys
Cambridge’s plural-noun guidance supports this consonant-plus-y distinction.
A Simple Test for Flys or Flies
When you’re writing quickly, you don’t need to stop and analyze the entire grammar of the sentence.
Use this three-step check.
Step 1: Are you talking about more than one fly?
If yes, write flies.
“There are several flies outside.”
Step 2: Is “fly” the action performed by he, she, or it?
If yes, write flies.
“The plane flies every afternoon.”
Step 3: Are you looking at “flys”?
In ordinary standard English, replace it with flies.
That’s the practical answer in nearly every everyday writing situation.
Case Study: Choosing the Correct Form in a Sentence
Consider this short paragraph:
“Every summer, flies enter the house through the open windows. One fly usually appears first. Then several more arrive. My cat watches them while the insects fly around the ceiling.”
There are several forms here, and each one has a different job.
Flies appears first as a plural noun because the writer refers to multiple insects.
Fly appears next as a singular noun because the writer refers to one insect.
Fly appears later as a base verb because the subject is plural: “the insects fly.”
This illustrates an important point: spelling depends on grammar and meaning, not just on the word itself.
Facts About the Word “Flies”
A few details make this spelling question more interesting than it first appears.
- Flies is the standard plural of fly in English.
- Flies also functions as the third-person singular present form of the verb fly.
- Flew is the simple past form of fly.
- Flown is the past participle.
- Flying is the present participle and gerund form.
- American and British English both use flies for the ordinary insect plural.
- British English uses flies in a clothing-related sense for the front opening of trousers.
- Theater professionals use the flies for the space above a stage.
Frequently Asked Questions
Is “flys” or “flies” the correct spelling?
Flies is the correct spelling in standard English. It is the plural form of the noun “fly” and the third-person singular form of the verb “fly.”
Why is “flys” incorrect in modern English?
Flys is generally a spelling error in modern English. For many words ending with consonant y, English uses the y to ies rule, changing “y” to “ies.”
What is the plural of “fly”?
The plural of fly is flies, especially when referring to the winged insect. For example, “Three flies are in the kitchen.”
How do you use “flies” as a verb?
Flies is the third-person singular present tense of the verb “fly.” For example, “She flies across the garden,” or “He flies a plane.”
How can I remember the spelling of “flies”?
Remember the spelling pattern for words ending with consonant y: change “y” to “ies” for the plural form. This rule helps improve writing accuracy and prevents common spelling mistakes.
Final Takeaway
Choosing flies over flys ensures correct spelling and follows standard English grammar rules. Remember the y to ies rule for the plural form, while flies also works as a third-person singular present tense verb. With this simple spelling pattern, you can improve writing accuracy, avoid common spelling errors, and use the correct word confidently.
