British English sometimes referred to as the Queen's English, is the common name for the standardized version of spoken and written English used in the countries of the United Kingdom and in most British Commonwealth nations. It differs from standard US English both in its phonology (pronunciation), spelling, and in some grammatical constructs (e.g. some words in US English which take the definite article "the" , such as Hospital or University, do not take an article in British English).
Differences in spelling between American and British English
Some American English spellings have been developed to follow more phonetic forms than in British English.
Words such as centre, theatre, and spectre are (usually) in American English spelled "center", "theater", and "specter".
American spellings tend to eliminate the 'u' in words which, in British English, are spelled with an 'our'. Example: color and colour, parlor and parlour, savior and saviour. However, there are exceptions to this, such as the word 'glamour' which is thus spelt in both dialects.
ae and oe
Many British words tend to retain the ligatures 'oe' and 'ae' in words of Greek or Latin origin. Examples: diarrhoea (American: diarrhea), orthopaedic (orthopedic), oesophagus (esophagus).
Many British words use the -xion ending rather than the -ction ending. Examples: reflexion (American: reflection), circumflexion (American: circumflection), deflexion (American:deflection).
Certain words have their consonants doubled in the British spelling when turned into gerunds. Examples: focussed (American: focused), worshipped (American: worshiped), targetted (American: targeted).
Hyphens and spacing
Words are usually compounded in American English (ex: counterattack, runoff), whereas in British English they are more likely to be separated by a hyphen (counter-attack, run-off).
ise/ising and ize/izing
In British English many words with the suffixes "ize" and "izing" can also be spelled with an "s" in place of the "z". This is largely a development seen from the latter half of the twentieth century to the extent that the use of "z" in many words is often mistaken in Britain and Ireland as an American trait. The Oxford English dictionary prefers the use of z whereas other British dictionaries may vary.