British spellings compared to American spellings

GENERAL RULES

Words ending in OUR have been changed to OR in America (e.g. colour)
Words ending in IOUR have been changed to IOR in America (e.g. behaviour)
Many words ending in YSE or ISE have been changed to YZE or IZE in America (e.g. analyse, categorise, standardise) Exceptions: ARISE, DEVISE
Many words ending in YSED or I SED have been changed to YZED or IZED in America (e.g. categorised, standardised)
Many words ending in ISATION have been changed to IZATION in America (e.g. categorisation, standardisation)
Words ending in RE have been changed to ER in America (e.g.centre, metre)
Words containing the silent letters OUGH have been changed to in America so they are spelt phonetically (e.g. doughnut, hiccough)
Words containing a double consonant before ING and ED have been changed to one consonant (e.g. travelling)
Words which vary in spelling according to whether they are nouns or verbs have been standardised in some cases. eg: verbs: practise, license (NOTE: the word standardised follows the ISED rule above)

British spellings compared to American spellings