An airplane (in British English, aeroplane) is one type of aircraft. But there are many other types, including helicopters, dirigibles, gliders, and microlights.
So, if you want to talk about flying vehicles in general, you could use aircraft, but for specific cases that are fixed-wing, powered aircraft, use airplane.
The full saying, “There’s no use crying over spilled milk,” means that we shouldn’t waste time regretting something that cannot be changed. There’s nothing that can be done once the milk is spilled except clean up and move on.
Spill is a regular verb in American English and irregular in British English. In American English, the simple past tense form and past participle are both spilled. British English shares the same past tense, but the past participle is spilt.
To make sure you have the right spelling of spilt or spilled, you can use the QuillBot Grammar Checker.
The answer is that it depends on where your audience is. In American English, analyzing is the correct form (along with the infinitive analyze). In British English, the word is spelled analyse.
In British English you are free to use either spelling, as neither is considered wrong. But it is important to remain consistent, not just with the spelling of analyze/analyse but in your whole document.
In American English, analyse would be considered a misspelling.
You can ensure you have the correct spelling of analyzing or analysing with the QuillBot Grammar Checker.
Buses is the correct spelling of both the plural of the noun bus and the third person singular of the verb bus. In both British English and American English, busses is a less common but still acceptable variant.
You can use the QuillBot Grammar Checker to ensure you have the correct spelling of buses.
The plural of the noun bus is either buses or busses. The usual spelling in both British English and American English is buses, although it is not incorrect if it is spelled busses.
You can check if busses or buses is the correct plural of bus by using the QuillBot Grammar Checker.
Bus is a verb meaning “transport by bus” or, in the US, “clear tables in a restaurant.” The past tense has two possible spellings: bused or bussed.
In both British English and American English, bused is preferred, but neither is wrong.
You can check that you have the correct spelling of bussed or bused by using the QuillBot Grammar Checker.
Busses is one of the two possible plural forms of the noun bus. It is also the third-person singular form of the verb bus. In both cases, the word can also be spelled buses.
In fact, most authorities suggest that in both British English and American English, the single “s” version is preferable.
There is also the somewhat rare American English verb buss meaning “kiss,” and busses is the third-person singular form of that verb.
To make sure you have the right spelling of busses or buses, you can use the QuillBot Grammar Checker.
If you have an axe to grind, it means you are holding a grudge or want to pursue a particular agenda (e.g., “Everyone could see that John had come to the meeting with an axe to grind”).
Having an axe to grind is an example of an idiom, where the meaning of the phrase is not what it says literally.
You can imagine that in a situation where there is a line of people waiting to use a public grind wheel, someone who is waiting to grind their axe will be a little impatient and focused on getting the job done. This is having an axe to grind.
In American English, axe and ax are interchangeable, so you may see the expression spelled as ax to grind.
A battle-axe or battleaxe (or, in the US, battle-ax) is traditionally an axe designed for use in battle. It is also a disparaging term for a woman who is seen as belligerent or bellicose. It is best avoided, seeing as it relies on a stereotype of a woman who is docile and gentle.
The battle-axe was used for many centuries across many cultures as a relatively cheap weapon that was simple to manufacture and could inflict devastating wounds.
The QuillBot Paraphrasing Tool can help you find alternatives to battle-axe to reflect your intended meaning.
Yes, axe is correct in American English, and is actually the more common spelling. However, some style guides require that it be spelled ax, so it is important to check.
And remember, being consistent is also important. Don’t switch between ax and axe. Choose one and stick to it.
Axe is a noun that describes a long-handled tool with a sharpened, wedge-shaped cutting head used to chop things (typically wood).
It is also a regular verb, describing the action of chopping with the eponymous tool.
To make sure you have the right spelling of ax or axe, you can use the QuillBot Grammar Checker.
When you “spill the beans,” you confess or share something that you know in confidence. It is somewhat informal and is unlikely to be used to describe, for example, betraying state secrets.
When you are using the past participle, bear in mind that it is spelled differently in American English and British English. In American English the past participle is spilled, and in British English it is spilt.
In the UK, the preferred spelling is analyse. In British English, it can be spelled either way, but the preferred way is analyse. In American English, analyze is the only correct spelling.
It is important to remember to remain consistent. Only use one spelling of analyze/analyse, and use either American English spellings or British English spellings throughout your document.
The QuillBot Grammar Checker can help you choose the correct spelling of analyze.
A carat is equivalent to 200 milligrams. It is a measurement used to describe the mass of diamonds. A common mistake is to think that it describes the dimensions of a gem, but this is not the case.
In British English, carat is also used to describe the purity of gold. In American English, it is usually spelled karat. In both cases, 24 carat/karat gold refers to 100 percent pure gold.
The QuillBot Grammar Checker can help you ensure you are using the correct spelling of carat/karat.
Yes, caret is a word. It is the name for this symbol: “^”. It is used in the publishing industry to indicate where an insertion needs to be made. It is sometimes written in subscript: “^”.
Although it is pronounced the same, its meaning is not related to carat or karat, which are terms used to measure gold and gemstones.
You can use the QuillBot Grammar Checker to ensure you use words like caret correctly.
In American English, the usual spelling is karat, although carat is also acceptable. In British English, the measurement of the purity of gold is spelled carat.
You can use the QuillBot Grammar Checker to ensure your spelling of carat/karat is correct.
Acknowledgement is a noun that means “recognition” (e.g., “Phil’s bonus was in acknowledgement/recognition of his successful campaign”).
Acknowledgement is spelled differently in British English (acknowledgement) and American English (acknowledgment).
If you are following a style guide, then make sure you use the correct form. If you are not following a guide, then the important thing is to be consistent in your use of British or American spellings.
The QuillBot Grammar Checker can help you maintain consistent spelling in your writing.
In the US, a bank account that issues a checkbook is a checking account. The equivalent account in the UK is called a current account, and it usually comes with a chequebook.
The spelling of check for every other meaning is the same in American English and British English.
You can make sure your spelling of check or cheque is correct using the QuillBot Grammar Checker.
In the USA, it is always check. British English uses cheque to refer to the personalized money order you use to purchase things or pay people.
For every other use in both British and American English, check is the correct spelling.
The QuillBot Grammar Checker can help you check your spelling of check or cheque.
It depends what country you are in! In the United Kingdom, the noun meaning a piece of paper printed by a bank that allows you to buy something or pay someone is spelled cheque. In American English, it is spelled check.
In every other use of check as either a noun or verb, the spelling is the same in American and British English.
You can use the QuillBot Grammar Checker to ensure you use check and cheque correctly.
Both “aging” and “ageing” are two acceptable spellings for the word that describes something as getting older or deteriorating.
In American English you spell it “aging.” In British English you spell it “ageing.”
You can use the QuillBot Grammar Checker to help you make the correct choice for your variety of English when faced with spelling variations like this.
Synonyms for the adjective aging include:
Synonyms for aging when it is used as the present participle (e.g., “He is aging”) include:
Use the QuillBot Paraphraser to discover alternatives to the adjective “aging” in your specific context.
Yes, focussed is correct in British English (and American English), but it is more usual these days for the simple past tense and past participle of this verb to be spelled focused. This is also true for American English.
While it is acceptable to use either spelling, it is best to make sure you only use one in any document to maintain consistency.
You can change the language settings in the QuillBot Grammar Checker to ensure you have the correct US or UK spelling of focussed or focused.
Airplane would be understood by users of British English, but it is likely to be considered an incorrect spelling or an “Americanism.” Although there is no difference in meaning between aeroplane and airplane, you should spell it to remain consistent with the spelling in the rest of your document.
The QuillBot Grammar Checker has selectable regional language options, so you can be sure you have the correct spelling of aeroplane/airplane.
No, mold is incorrect in British English. The correct spelling for both the noun and the verb is mould. Mold is the correct American English spelling.
This is also true for all related words such as mouldy, moulder, and the verb forms moulds, moulded, moulding.
You can choose different regional settings in the QuillBot Grammar Checker to make sure you have the correct spelling of mold or mould.
The only difference between mold and mould is that mold is the correct spelling in American English, and in British English it is spelled mould.
This is true of the verb and the noun. As a verb, mold/mould means “shape something or someone” or “become moldy/mouldy.”
The noun mold/mould means the physical object used to form something (e.g., plastic) into a specific shape, or it refers to the fungal growth found in damp places.
The QuillBot Grammar Checker has selectable language regions, so you can always be sure you have the correct spelling of mold or mould.
Although aluminium is recognized in dictionaries as a variant spelling of aluminum, some style guides (e.g., APA) require the more common American English spelling, aluminum.
Generally, aluminum is the standard spelling in North America, while aluminium is prevalent in the rest of the English-speaking world.
The QuillBot Grammar Checker lets you select your language region so you can check if you have the correct spelling of aluminum or aluminium.
Aluminum is recognized as a variant spelling of the more common aluminium in British English.
Although it can be spelled either way, it’s usually wisest to use the preferred geographical spelling for your audience. And remember to use the spelling required by your institution’s style guide.
For instance, the APA Publication Manual requires aluminum, except when quoting a source text, whereas the Chicago Manual of Style recommends spelling according to whether you are following American English or British English spellings.
With the QuillBot Grammar Checker, you can select your language region preferences, so you can ensure that you have the correct spelling of aluminum or aluminium.
Counselor is spelled counsellor in British English. It has the same meaning of “someone who gives counsel or advice,” but it is not used in the UK to refer to a lawyer or legal representative.
In a British court, you will be represented by a “solicitor,” a “barrister,” or, in Scotland, an “advocate.”
You can set the language region of the QuillBot Grammar Checker to ensure you have the correct spelling of counselor or counsellor.
In American English, a councilor is someone who is a member of a council. A counselor is someone who gives counsel or advice or a legal representative.
In British English, these words are spelled councillor and counsellor, but the latter is not used to describe a legal representative or lawyer.
The QuillBot Grammar Checker has language settings to allow you to choose the correct region and make sure you have the correct spelling of councilor or counselor.
It doesn’t matter whether you are using American English or British English because you can use both focussing and focusing in either variant. However, it is much more common to find the single “s” spelling, focusing.
This is also true for the simple past tense and past participle of the verb “focus.” This can be spelled focussed or focused, with the single “s” version also by far the more common form.
The QuillBot Grammar Checker has selectable language options to make sure you have the correct US or UK spelling of focussed or focused.
There’s no difference in meaning between cancelled and canceled; they’re just two different spellings of the same word, the past tense of the verb “cancel.”
Cancelled (double “l”) is the standard spelling in British English, canceled (single “l”) in American English.
Make sure to pick the spelling appropriate to the context you’re writing in and stick to it consistently. The QuillBot Grammar Checker can help you with this.
In the UK, the more common spelling is recognise, although recognize is also correct.
In American English, only recognize is correct. In British English, it can be spelled either way, but make sure you choose one or the other and stick with it.
The QuillBot Grammar Checker lets you select American English or British English, so you can ensure that you have the correct regional spelling of recognise or recognize.
Recognise is the more common British English spelling of recognize. It is considered incorrect in American English.
Most words that end in “-ize” are more usually spelled “-ise” in British English, although the Oxford University Press and Oxford English Dictionary prefer “-ize.”
Whichever way you spell it, recognise/recognize is a regular verb that means “identify something or someone that is already known” (e.g., “Hai wasn’t sure his teacher would recognise/recognize him after so long”) or “acknowledge someone’s efforts or achievements” (e.g., “The award was given every year to recognise/recognize the most community-minded student”).
You can select the regional variation in the QuillBot Grammar Checker to ensure you have the correct spelling of recognise or recognize.
In American English, the spelling is data center or datacenter, and in British English, it is data centre. This simply follows how the word center/centre is spelled in the US and UK. This difference is also seen in word pairs such as theater/theatre and meter/metre.
Center/centre is both a noun and a verb, and the spelling remains consistent for those two word classes.
As a noun, center/centre can be a physical place (e.g., “London is a center/centre for dance and the arts”), a description of a mathematical point (e.g., “The center/centre of a circle”), or a figurative place (e.g., “From the day he was born, Hugo has always been at the center/centre of our world”).
The QuillBot Grammar Checker can ensure you are using the correct American or British English spelling of data center/centre.
In American English, it is exam center, and in British English, it is exam centre. That simply reflects how the word center/centre is spelled in the two different variants of the language. This difference is also seen in word pairs such as theater/theatre and meter/metre.
Center/centre is a noun that refers to the literal or figurative middle of something or, as in the case of “exam centre/centre,” to a building that serves a particular purpose.
As a verb, center/centre means “place or be in the middle or at the heart of something.”
You can use the QuillBot Grammar Checker to ensure you use center or centre correctly.
Neighbor is the correct spelling in American English. In British English, it is spelled neighbour. It is one of a number of words ending in “-or” in American English that are spelled “-our” in British English.
Other words include:
You can check if you have the correct spelling of neighbor or neighbour with the QuillBot Grammar Checker.
In American English, it is neighborly, and in British English, it is spelled neighbourly.
The two spellings of this adjective are not interchangeable—the American spelling is incorrect in British English and vice versa.
You can ensure you have the proper spelling of neighborly or neighbourly with the QuillBot Grammar Checker.
It depends on where your audience is! In American English, the correct spelling is neighborhood, and in British English, it is neighbourhood.
It is important to maintain consistency with how words are spelled, so if your document uses American English spellings, it should apply to all words.
You can check if you have the correct spelling of neighborhood or neighbourhood with the QuillBot Grammar Checker.
It depends on where your audience is located. In British English, the correct spelling is flavourful, and in American English, it is flavorful.
The “-our” or “-or” difference also holds true for the noun, verb, and adjective flavour/flavor, and all the forms of the verb (e.g., flavouring/flavoring).
The QuillBot Grammar Checker will help you to ensure that you have the correct spelling of flavour or flavor.
In British English, the adjective is spelled flavoured, and in American English, it is spelled flavored. This is also the spelling for the simple past tense form and past participle.
The same is true of other forms of the verb flavour/flavor: flavours/flavors, flavouring/flavoring.
You can use the QuillBot Grammar Checker to ensure you have the correct spelling of flavour or flavor.
Realise and realize are two spellings of the same verb. The spelling depends on the type of English.
Indian English generally follows the UK guidelines for spelling, so realise is standard.
The same difference applies to similar words, such as recognize or recognise, analyze or analyse, finalize or finalise, minimize or minimise, and organize or organise.
It’s important to choose one and use it consistently. The QuillBot Grammar Checker can help you with this.
Judgment and judgement are two spellings of the same noun. The spelling depends on the type of English.
It’s important to choose one and use it consistently. The QuillBot Grammar Checker can help you with this.
Judgment and judgement are two spellings of the same noun. The spelling depends on the type of English.
AP style follows American English guidelines, so judgment (without an “e”) is correct.
It’s important touse one spelling consistently. The QuillBot Grammar Checker can help you with this.
Travelling and traveling are two spellings of the same verb. The spelling depends on the type of English you use:
It’s important to choose one and use it consistently. The QuillBot Grammar Checker can help you with this.
Travelling and traveling are two spellings of the same verb. The spelling depends on the type of English you use:
It’s important to choose one and use it consistently. The QuillBot Grammar Checker can help you with this.
Travelling and traveling are two spellings of the same verb.
In this context, it refers to a violation that takes place when a basketball player takes too many steps without dribbling the ball.
The spelling depends on the type of English you use:
It’s important to choose one and use it consistently. The QuillBot Grammar Checker can help you with this.
Offence and offense are two spellings of the same noun. The spelling depends on the type of English.
The same difference applies to similar words, such as defence or defense, licence or license, and pretence or pretense.
It’s important to choose one spelling and use it consistently. The QuillBot Grammar Checker can help you with this
Offence and offense are two spellings of the same noun. The spelling depends on the type of English.
The same difference applies to similar words, such as defence or defense, licence or license, and pretence or pretense.
It’s important to choose one spelling and use it consistently. The QuillBot Grammar Checker can help you with this.
Offence and offense are two spellings of the same noun. The spelling depends on the type of English.
The same distinction applies to similar words, such as defence or defense, licence or license, and pretence or pretense.
It’s important to choose one spelling and use it consistently. The QuillBot Grammar Checker can help you with this.
Realise and realize are two spellings of the same verb. The spelling depends on the type of English.
Canadian English usually follows the UK guidelines for spelling, but for words ending in -ize or -yze, it follows American guidelines. This means realize is standard.
The same difference applies to similar words, such as recognize or recognise, analyze or analyse, finalize or finalise, minimize or minimise, and organize or organise.
It’s important to choose one and use it consistently. The QuillBot Grammar Checker can help you with this.
Labor and labour are two spellings of the same noun. The spelling depends on the type of English.
The same difference applies to similar words, such as “behaviour or behavior,” “honor or honour,” “color or colour,” “favorite or favourite,” “favor or favour,” and “humor or humour.”
It’s important to choose one type of English and use it consistently. The QuillBot Grammar Checker can help you with this.
American English is used in the US, while British English is used in the UK. The main differences between American English and British English relate to:
There are also many differences in pronunciation and colloquial language that are not relevant in the context of formal writing.
Spelling in English was not standardized before the 18th century, meaning that many words had several different spellings. In 1755, Samuel Johnson’s Dictionary of the English Language was published in the UK, standardizing spellings for the first time.
Meanwhile, Noah Webster’s American Dictionary of the English Language (the ancestor of Merriam-Webster) appeared in 1828 in the US. Webster disagreed with Johnson on various points of spelling, and Webster’s dictionary, not Johnson’s, was adopted as a guide to standard spelling for American English.
Neither Johnson nor Webster invented the spellings they recommended for British and American English; rather, they looked at the spellings that were in common use at the time and made decisions about which ones they regarded as most widespread and reasonable.
Different national variants of a language tend to develop differences because they evolve in isolation from each other over time. With modern globalization and American cultural influence, these differences are becoming smaller, although they still exist.
Dreamed and dreamt are two spellings of the same verb. They’re both common, depending on the variant of English:
In both cases, the other variant of this past-tense verb is also considered acceptable. It’s important to choose one and use it consistently. The QuillBot Grammar Checker can help you with this.
Dreamed and dreamt are two spellings of the same verb. They’re both common, but dreamt is more common in British English (whereas dreamed is more common in American English).
It’s important to choose one and use it consistently. The QuillBot Grammar Checker can help you with this.
Dreamed and dreamt are two spellings of the same verb. They’re both common, depending on the variant of English:
In both cases, the other variant of this past-tense verb is also considered acceptable. It’s important to choose one and use it consistently. The QuillBot Grammar Checker can help you with this.
Humor and humour are two spellings of the same noun or verb. The spelling depends on the type of English.
Australian English mostly follows British English guidelines, so humour is correct.
The same difference applies to similar words, such as “behavior or behaviour,” “labor or labour,” “favor or favour,” “favorite or favourite,” “color or colour,” and “honor or honour.”
It’s important to choose one and use it consistently. The QuillBot Grammar Checker can help you with this.
Humor and humour are two spellings of the same noun or verb. The spelling depends on the type of English.
“Vitreous humour/humor” refers to the clear, gelatinous mass that fills the space in the eye between the retina and lens.
The same difference applies to similar words, such as “behavior or behaviour,” “labor or labour,” “favor or favour,” “favorite or favourite,” “color or colour,” and “honor or honour.”
A QuillBot grammar check can help you use either “humor” or “humour” correctly.
Humor and humour are two spellings of the same noun or verb. The spelling depends on the type of English.
The same difference applies to similar words, such as “behavior or behaviour,” “labor or labour,” “favor or favour,” “favorite or favourite,” “color or colour,” and “honor or honour.”
A QuillBot grammar check can help ensure you’re using either “sense of humor” or “sense of humour” consistently.
Honor and honour are two spellings of the same noun or verb. The spelling depends on the type of English.
The same difference applies to similar words, such as “behavior or behaviour,” “labor or labour,” “favor or favour,” “favorite or favourite,” “color or colour,” and “humor or humour.”
A QuillBot grammar check can help ensure you’re using one type of English consistently.
Toward and towards are two spellings of the same preposition. The spelling depends on the type of English.
It’s important to choose one and use it consistently. The QuillBot Grammar Checker can help you with this.
Cancelled and canceled are two correct spellings of the past tense verb “to cancel.” However, AP style advises to use canceled, with one “l”, because this is common in American English.
It’s important to choose one and use it consistently. The QuillBot Grammar Checker can help you with this.
Theatre and theater are two spellings of the same noun.
They’re both pronounced [thee-uh-ter], despite the difference in spelling. However, the pronunciation may vary slightly depending on regional dialect. For example, in American English, the final syllable may be pronounced with a “d” sound instead of a “t” sound: [thee-uh-der].
It’s important to choose one type of English and use it consistently. The QuillBot Grammar Checker can help you with this.
Theatre and theater are different spellings of the same noun. Its spelling depends on the type of English you use.
This is also true for similar words, such as center or centre, meter or metre, liter or litre, saber or sabre, and fiber or fibre.
It’s important to choose one type of English and use it consistently. The QuillBot Grammar Checker can help you with this.
Theatre and theater are spelled differently in American and British English.
AP style follows American English guidelines, so theater is the correct way to spell the noun.
This is also true for similar words, such as center or centre, meter or metre, liter or litre, saber or sabre, and fiber or fibre.
It’s important to choose one type of English and use it consistently. The QuillBot Grammar Checker can help you with this.
PhD advisor and PhD adviser are both equally correct. It’s important to be consistent throughout your writing, whether you choose advisor or adviser.
The QuillBot Grammar Checker can help you with consistency and other problems!
College adviser and college advisor are both equally correct. It’s important to be consistent throughout your writing, whether you choose advisor or adviser.
The QuillBot Grammar Checker can help you with consistency and other problems!
Financial advisor and financial adviser are both equally correct. It’s important to be consistent throughout your writing, whether you choose advisor or adviser.
The QuillBot Grammar Checker can help you with consistency and other problems!
Both “I can’t love you anymore” and “I can’t love you any more” are correct, but they mean two different things.
When you have to pick between anymore and any more, you need to determine whether you want to indicate time (anymore) or a quantity (any more).
The QuillBot Grammar Checker can automatically fix your mistakes for free!
Not anymore and not any more are both correct, but the variant you have to use depends on the context. You can follow these rules of thumb to pick between anymore and any more:
The QuillBot Grammar Checker can automatically fix your mistakes for free!
Honor and honour are two spellings of the same noun or verb. The spelling depends on the type of English.
The same difference applies to similar words, such as “behaviour or behavior,” “labor or labour,” “color or colour,” “favorite or favourite,” “favor or favour,” and “humor or humour.”
It’s important to choose one type of English and use it consistently. The QuillBot Grammar Checker can help you with this.
Toward and towards are two spellings of the same preposition. The spelling depends on the type of English.
It’s important to choose one and use it consistently. The QuillBot Grammar Checker can help you with this.
Toward and towards are two spellings of the same preposition. The spelling depends on the type of English.
AP style generally follows American English conventions, so they favor toward.
It’s important to choose one and use it consistently. The QuillBot Grammar Checker can help you with this.
Behaviour and behavior are two spellings of the same noun. The spelling depends on the type of English.
Australian English mainly follows UK guidelines, so behaviour is the correct spelling.
The same difference applies to similar words, such as “honor or honour,” “labor or labour,” “favor or favour,” “favorite or favourite,” “color or colour,” and “humor or humour.”
It’s important to choose one type of English and use it consistently. The QuillBot Grammar Checker can help you with this.
Behaviour and behavior are two spellings of the same noun. The spelling depends on the type of English.
Canadian English mainly follows UK guidelines, so behaviour is the correct spelling.
The same difference applies to similar words, such as “honor or honour,” “labor or labour,” “favor or favour,” “favorite or favourite,” “color or colour,” and “humor or humour.”
It’s important to choose one type of English and use it consistently. The QuillBot Grammar Checker can help you with this.
Favourite and favorite are two spellings of the same noun, adjective or verb. The spelling depends on the type of English.
Indian English mostly follows British English guidelines, so favourite is standard.
The same distinction applies to similar words, such as “honor or honour,” “labor or labour,” “favor or favour,” “behavior or behaviour,” “color or colour,” and “humor or humour.”
It’s important to choose one type of English and use it consistently. The QuillBot Grammar Checker can help you with this.
Favourite and favorite are two spellings of the same noun, adjective or verb. The spelling depends on the type of English.
Canadian English mainly follows British English guidelines, so favourite is the correct spelling.
The same distinction applies to similar words, such as “honor or honour,” “labor or labour,” “favor or favour,” “behavior or behaviour,” “color or colour,” and “humor or humour.”
It’s important to choose one type of English and use it consistently. The QuillBot Grammar Checker can help you with this.
Labor and labour are two spellings of the same noun. The spelling depends on the type of English.
The same difference applies to similar words, such as “behaviour or behavior,” “honor or honour,” “color or colour,” “favorite or favourite,” “favor or favour,” and “humor or humour.”
A QuillBot grammar check can help ensure you’re using one type of English consistently.
Labor and labour are two spellings of the same noun. The spelling depends on the type of English.
The same difference applies to similar words, such as “behaviour or behavior,” “honor or honour,” “color or colour,” “favorite or favourite,” “favor or favour,” and “humor or humour.”
QuillBot’s grammar check tool can help ensure you’re using “Labor Day” or “Labour Day” consistently.