The United States and United Kingdom are "two countries divided by a common language".
George Bernard Shaw

This week we will look at the spelling differences between American English (God bless America) and British English (God save the Queen).
Last week the reasons was explained for the differences between the American English and British English. So, this week you might ask: what causes the differences in spellings?
Well, even though the English language originated in Britain, it is said that dictionary makers drove the American spelling changes. According to Wikipedia:
Noah Webster wrote the first American dictionary in 1828. At the time America was a relatively new country and Webster's particular contribution was to show that the region spoke a different dialect from Britain, and so he wrote a dictionary with many spellings differing from the standard. Webster initiated many of these changes unilaterally.

In spite of Americans changing things in order to be different from the British the English spelling rules (and for any different variety of the English language) are complex, with many exceptions. You can however, check your spellings by; spell check the document if it is electronic, ask someone you trust to review your written document, re-read the written document carefully for errors, use a dictionary (most dictionaries contain the spelling of its derivatives: plural forms and participles and even the correct pronunciation of the word) and finally, learn the basic spelling rules of spelling. It is important to point out that, if you are using the British English make sure you use a British English dictionary and likewise, if you are using the American English make sure also that you use an American English dictionary. It is important to be consistent with the use of the same word if there is a difference in spelling. Remember, whatever English you are using make sure to keep the preferences of who you will be writing for in mind and that it is the appropriate form to use. This you will find necessary if you write, travel, live, work and study in other countries that use its own preference of the variety of the English language.

The list below is showing a general spelling differences between the American and British English. The list is placed in alphabetical order and is not comprehensive. Further down you will see another group of lists, highlighting some of the changes that cause the differences in spelling.

American                           British

A                                     
aging                              ageing
aluminum                           aluminium
analog                             analogue
analyze                            analyse
annex                              annexe                            
anymore                            any more
argument                           arguement
ass                                arse
artifact                           artefact                           
ax /axe                            axe                                 

B
behoove                            behove
B.S.                               B.Sc.
buret, burette                     burette

C
carburetor                         carburettor
check                              cheque
cipher                             cypher                              
clamor                             clamour
color                              colour
connection                         connection/
                             connexion
criticize                          criticise
D
defense                            defence
diarrhea                           diarrhoea
disk                               disc                                   
dispatch                           despatch
donut/ doughnut                    doughnut
draft                              draught                             
Dr.                                Dr(no full stop)

E
emphasize                          emphasise
encyclopedia                       encyclopedia

F
favor                              favour
fetus                              foetus
flutist                            flautist
forever                            for ever
fulfill/fulfil                     fulfil                         
furor                              furore                              

G
gauge, gage                        gauge
glycerin                           glycerine
gonorrhea                          gonorrhoea
gray                               grey

H
harbor                             harbour
harmonize                          harmonise
hauler                             haulier
hemorrhage                         haemorrhage
homeopathy                         homoeopathy
humor                              humour

I
initialize                         initialise
installment                        instalment

J
jewelry                            jewellery                           
judgment                           judgement

K
kilometer                          kilometre

L
learned                            learnt/learned
license                            licence(noun)
loath                              loth


math                               maths
mold                               mould
molt                               moult
mom(my)                            mum(my)

N
neighbor                           neighbour
net                                net/nett
                          (amt.of money)
neuron                             neurone

O
offense                            offence
omelet, omelette                   omelette
organization                       organisation
optimize                           optimise

P
pajamas                            pyjamas
peddler                            pedlar
pediatrics                         peadiatrics
pedophile                          peadophile
persnickety                        pernickety
plow                               plough
program                            programme


Q

R
rancor                             rancour
realize                            realise
recognize                          recognise
rigor                              rigour

S
savior                             saviour
scalawag                           scallywag
shivaree                           charivari
skeptic(ism/al)                    sceptic(ism/al)
smelled                            smelt/smelled
snicker                            snigger
specialty                          speciality
story                              storey
sulfur                             sulphur

T
theater                            theatre
tidbit                             titbit
tire                               tyre
toward                             towards
traveling/travelling               travelling


U
uh, um                             er, erm

V
vigor                              vigour
vise                               vice
visualize                          visualise

W
wagon                              waggon
woolen                             woollen

X

Y
yogurt                             yoghurt

Z

Some of the changes that cause the differences
in spelling.


The change of compound consonants into simple
consonants.

American                           British
check (bank)                       cheque
draft (ship’s)                     draught
plow                               plough
vial                               phial

The omission of a redundant “e”
American                           British
asphalt                            asphalte
ax                                 axe
good-by                            goodbye
story (of a house)                 storey

The change of terminal “-re” into “-er”
American                           British
center                             centre
fiber                              fibre
meter                              metre
theater                            theatre

The omission of unaccented foreign terminations.
American                           British
catalog                            catalogue
envelop                            envelope
program                            programme
prolog                             prologue

The omission of the penultimate u in words ending
in “-our”

American                           British
behavior                           behaviour
color                              colour
flavor                             flavour
honor                              honour
neighbor                           neighbour
odor                               odour

The omission of u when combined with “a” or “o”

American                           British
mold                               mould
mustache                           moustache
stanch                             staunch

The change of “o” into “a”
American                           British
naught                             nought
slug (verb)                        slog
slush                              slosh

The conversion of decayed diphthongs into simple
vowels.
American                           British
anemia                             anaemia
encyclopedia                       encyclopeadia
hemorrhage                         haemorrhage
medieval                           mediaeval

The change of “e” into “i”
American                           British
inclose                            enclose
indorse                            endorse
inquire                            enquire

The reduction of duplicate consonants to single
consonants.
American                           British
councilor                          councillor
jewelry                            jewellery
fagot                              faggot
wagon                              waggon

The change of “c” into “s”
American                           British
defense                            defence
offense                            offence
pretense                           pretence
vise (a tool)                      vice

The substitution of “s” for “z”
American                           British
advertisement                      advertizement
fuse                               fuze
organization                       organization

The substitution of “k” for “c”
American                           British
mollusk                            mollusc
skeptic                            sceptic

The substitution of “y” for “i”

American                          British
dryly                             drily
gypsy                             gipsy
The change of y into “a“, “ia” or “i”
American                          British
baritone                          barytone
cider                             cyder
pajamas                           pajamas
siren                             syren
tire (noun)                       tyre

The substitution of “ct” for “x”
American                          British
connection                        connexion
inflection                        inflexion

The insertion of a supernumerary “e”
American                          British
forego                            forgo
foregather                        forgather

                            -ed vs. -t
verbs that use “-ed” or “-t “for the simple past
and past participle.

(These forms do not  exist for every verb.
The British also use “ed” for the past tense.
There are also other variation).

American                          British
dreamed                           dreamt
leaped                            leapt
learned                           learnt

Related articles:
English Idioms - English phrases and their meanings
Latin Abbreviations and their English meaning
Languages by Countries
Differences between American and British English - PT. 1