The main differences between US and UK English

When writing your dissertation, research paper or essay, you will have to consistently follow the conventions of a specific style of English. The most commonly used forms are American English, British English and Australian English. Although these dialects follow many of the same rules, they also have some important differences in spelling, punctuation and word choice. 

Check with your supervisor or department to find out if you are expected to use a specific style of English. If you are allowed to choose, pick the style that feels most natural to you. Make sure you set the correct proofing language for your document (in Microsoft Word, select “Review” and then “Language”).

Why is it so complicated?

After winning their independence from the British, Americans used language as a way to create their own identity. This led to many variations in spelling and punctuation, among other things. Australia also developed its own written conventions, which lie somewhere between those of the US and the UK (although they tend to be more British).

Of the three, Australian English is generally the most flexible, and US English is the least flexible. Bear in mind that the rules are not always very firm: there are many exceptions, and the preferred conventions are constantly changing!

Spelling

As the table below shows, the difference between UK and US spelling usually relates to just one or two letters.

US UK Australia
uses -ize, -yze (e.g. quantize, analyze) prefers -ise, -yse (e.g. quantise, analyse), but is flexible almost always uses ise, yse
-er (e.g. center, meter, etc.) -re (e.g. centre, metre, etc.) British usage
uses -or (e.g. honor, color, splendor) uses -our (e.g. honour, colour, splendour) British usage
uses –ction (e.g. connection) acceptable to use –xion (e.g. connexion), but this is increasingly rare American usage
often drops -e for word modifications (e.g. judge to judgment, live to livable) generally keeps e for word modifications (e.g. judge to judgement, live to liveable) keeps -e (e.g. judgement), like British; but sometimes drops -e (e.g. livable)
usually prefers -e to -oe or -ae (e.g. pediatrician, leukemia) uses -oe and -ae (e.g. paediatrician, leukaemia) British usage

The following cheat sheet outlines the preferred spelling of some words that are commonly used in academic writing.

Verbs
US UK Australia
analyze analyse analyse
apologize apologise apologise
capitalize capitalise capitalise
categorize categorise categorise
characterize characterise characterise
colonize colonise colonise
endeavor endeavour endeavour
enroll enrol enrol
fulfill fulfil fulfil
globalize globalise globalise
honor honour honour
hypothesize hypothesise hypothesise
inquire enquire enquire
install instal install
legalize legalise legalise
maneuver manoeuvre manoeuvre
maximize maximise maximise
minimize minimise minimise
mold mould mould
neutralize neutralise neutralise
optimize optimise optimise
paralyze paralyse paralyse
plow plough plough
privatize privatise privatise
randomize randomise randomise
realize realise realise
recognize recognise recognise
Past-tense verbs
US UK Australia
canceled cancelled cancelled
channeled channelled channelled
labeled labelled labelled
modeled modelled modelled
traveled travelled travelled
Nouns
US UK Australia
acknowledgment acknowledgement (either)
aluminum aluminium aluminium
artifact artefact artefact
behavior behaviour behaviour
caliber calibre calibre
center centre centre
color colour colour
cooperation co-operation (either)
councilor councillor councilor
counselor counsellor counselor
defense defence defence
estrogen oestrogen oestrogen
fetus foetus foetus
fiber fibre fibre
flavor flavour flavour
humor humour humour
judgment judgement judgement
labor labour labour
leukemia leukaemia leukaemia
license licence licence
liter litre litre
meter metre metre
neighbor neighbour neighbour
organization organisation organisation
paleontology palaeontology palaeontology
program programme (but program if computer-related) program
sulfur sulphur sulphur
theater theatre theatre
tire tyre tyre
vapor vapour vapour
Adjectives
US UK Australia
aging ageing ageing
favorite favourite favourite
gray grey grey
livable liveable livable
movable moveable moveable
orthopedic orthopaedic orthopaedic
salable saleable saleable
skeptical sceptical sceptical
somber sombre sombre

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Punctuation

The main punctuation differences relate to single and double quotation marks and where to place other punctuation in relation to quotations.

US UK Australia
Double quotation marks (“x”), but alternate with single for quotations within quotations (e.g. She said, “This model has been called ‘the best.’”) Single quotation marks (‘x’), but alternate with double for quotations within quotations (e.g. She said, ‘This model has been called “the best”’.) UK usage
Punctuation appears within quotation marks (e.g. “The best there is,” she said. or She said, “the best there is.”) except when punctuation emphasizes the writer’s sentence rather than the speaker’s quotation (e.g. Did she say, “the best there is”? or She told them we are “the best there is”!) Punctuation appears outside quotation marks, except when the punctuation is part of the original quotation (e.g. ‘The best there is’, she said. but She said, ‘the best there is.’; also, Did she say, ‘the best there is’? but She asked, ‘the best there is?’) UK usage

Verb conjugation

There are some differences in subject-verb agreement with collective nouns (nouns referring to a group of individual things as a unified whole) and in past tense verb forms.

US UK Australia
Tends to treat collective nouns as singular (e.g. The team is going to winthe staff has decided) Tends to treat collective nouns as plural (e.g. The team are going to win, the staff have decided) US usage
Verbs take -ed endings for simple past tense and past participles (e.g. compel to compelled, spell to spelled, learn to learned), with the exception of common irregular verbs (e.g. take to took, hear to heard)  Verbs take -ed endings for simple past tense and past participles, but with more exceptions (e.g. compel to compelled but spell to spelt, learn to learnt); irregular verbs are conjugated the same UK usage

Abbreviations

There is also disagreement over how to use periods in abbreviations.

US UK Australia
Most title abbreviations take a period (e.g. Doctor to Dr., Mister to Mr.Honorable to Hon., Drive to Dr.) Title abbreviations take a period only if the abbreviation does not end on the last letter of the full word (e.g. Doctor to Dr, Mister to Mr, but Honourable to Hon., Drive to Dr.) UK usage

Consistency is key

Most importantly, each individual word must be spelled the same throughout your document. However, it’s also best to avoid mixing different styles of English.

Examples:
  • The defense minister first travelled to China in 2013. (US English/UK English)
  • The defense minister first traveled to China in 2013. (US English)
  • The defence minister first travelled to China in 2013. (UK English)

In addition, the same spelling should generally be used for all forms of a word.

Examples:
  • The organization is headquartered in Osaka, but it usually organizes workshops in Tokyo. (US English)
  • The colours of the samples varied greatly, but the smallest sample was the most colourful. (UK English)
Is this article helpful?
Bas Swaen

Bas is co-founder of Scribbr. Bas is an experienced academic writer and loves to teach. He helps students by writing clear, simple articles about difficult topics.

6 comments

Martha Perry
April 16, 2019 at 10:17 AM

Your UK example for abbreviations is wrong. "Ave." for "Avenue" does indeed end with the same letter as the full word ("Av...e").

Also, those parentheticals are ambiguous: does the final period denote an abbreviation? Or does it simply denote the end of the sentence (following an abbreviation that does not take a period)?

Reply

Shona McCombes
Shona McCombes (Scribbr-team)
April 18, 2019 at 3:57 PM

Hi Martha, thanks for pointing out this error! The example has now been fixed :)

The final periods denote abbreviations. Consistent with the rest of the article, there are no sentence-ending periods in the parenthetical examples.

Reply

Ally B
February 24, 2018 at 7:48 PM

Dears,
Thanks for this. FYI - a spelling mistake (typo) appears in your first listed table:
"hypothesize | hypothesise|hyphothesise" - the third instance (Australian spelling) has an errant 'h' after the 'p'.
You're welcome!

Reply

Leon Smits
Leon Smits (Scribbr-team)
February 26, 2018 at 1:44 PM

Hi Ally,

Thanks!
We'll change that. :)

Cheers,
Leon

Reply

Francisco Sousa
February 16, 2018 at 3:50 AM

Thank this amazing thesis

Reply

Kris
June 16, 2016 at 8:00 PM

Thank you, this was amazing.

Reply

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