American English vs. British English in Research Manuscripts: A Free Guide

In a simpler world, English would be written the same way everywhere. However, when Noah Webster set out to create an American English dictionary in the early 1800s, he did more than just add new words to British English: he also revised the spelling of many common words to eliminate what he saw as unnecessary letters. His new spellings were adopted in the US but not the UK, and these spelling differences remain to this day.

The list below is intended to provide an overview of the most common spelling differences between British and American English. The words beginning each list are intended to establish overall patterns, whereas the words in italics towards the end of the lists are examples of deviations from the rule. Remember that you can choose between “English (U.S.)” and “English (U.K.)” in Microsoft Word when setting the language for your document. This change allows the spell check to help catch these differences in spelling.

Click here to download a list of American English and British English spelling differences for future reference.

-ize (-yze)/-ise

American/British

characterize/characterise

prioritize/prioritise

specialize/specialise

analyze/analyse

catalyze/catalyse

size/size

exercise/exercise

The products of the catalyzed reaction were characterized using specialized equipment/The products of the catalysed reaction were characterised using specialised equipment.

-or/-our

American/British

behavior/behaviour

color/colour

favor/favour

contour/contour

Because of its decolorization behavior, this material is favored/Because of its decolourisation behaviour, this material is favoured.

-er/-re

American/British

center/centre

fiber/fibre

liter/litre

parameter/parameter

Five milliliters of the mixture containing the fibers was pipetted on the center of the slide/Five millilitres of the mixture containing the fibres was pipetted on the centre of the slide.

e/(ae or oe)

American/British

ameba/amoeba

anesthesia/anaesthesia

diarrhea/diarrhoea

leukemia/leukaemia

cesium/caesium

The patient with leukemia was given anesthesia before the procedure/The patient with leukaemia was given anaesthesia before the procedure.

-se/-ce

American/British

defense/defence

practice (noun and verb)/practice (noun)/practise (verb)

license (noun and verb)/licence (noun)/license (verb)

defensive/defensive

advice (noun) and advise (verb)/advice (noun) and advise (verb)

The defense attorney had practiced law for over thirty years/The defence attorney had practised law for over thirty years.

-/e, -og/-ogue

American/British

aging/ageing

acknowledgment/acknowledgement

judgment/judgement

analog/analogue

dialog/dialogue

dying/dyeing (from die/dye)/dying/dyeing (from die/dye)

The aging analog-to-digital converter is slowly dying/The ageing analogue-to-digital converter is slowly dying.

-l/-ll OR -ll/-l

American/British

fulfill/fulfil

enroll/enrol

skill, skillful/skill, skilful

labeled/labelled

signaling/signalling

propelled/propelled

revealing/revealing

The skillful student noted that the drop in enrollment may be signaling a problem with the study design. The skilful student noted that the drop in enrolment may be signalling a problem with the study design.

This list of differences between American English and British English is by no means exhaustive, but we hope that it helps give you an idea of the distinctions between the two styles of writing. For guaranteed correct word usage, trust one of our editors to edit your manuscript. If you have questions about any particular word, please contact us.