American vs.British English
Some major journals including any of the Naturejournals, The Lancet,and BMJuse British spelling. In fact any journal from the UK, Australia, or New Zealand will use British spelling.
While it is not vital to use the correct style of spelling, in the interests of making the Editors job easier, it is good to match your spelling with that of the journal to which you are submitting.
Words differ in seven general ways from American to British spelling:
1. ending -or may be -our;
2. e may be oe;
3. or e may be ae;
4. ending -ize is usually -ise;
5. ending -er may be -re;
6. f may be ph;
7. an -ical ending may be reduced to -ic in American spelling.
See the table below for some examples of this, or go to a comprehensive list of American vs. British spelling