American spelling

Sensibly, the Americans use –ize/-ization  endings instead of –ise/-isation  (realize, nationalize, modernize, capitalization). Less known is that the Oxford English Dictionary, also uses –ize. 

I blame Bill Gates. When you put your spell-checker to UK English, Microsoft Word tells you to use ­–ise, even though this is not an absolute standard. In any case, always use –ize/-ization unless the preceding letter is a “y” (analyse, catalyse). If the preceding letter is a "y", then Americans will sometimes, but not always, use an “s” 

The American standard is –or rather than –our (color, honor, harbor as opposed to colour, honour and harbour.

Americans wisely write center, meter, liter, theater, whereas the British, apparently believing  themselves French, write centre, metre, litre, theatre.

Offense and  defense (USA) rather than  Offence, defence (UK)  (plus a few others).

But  Practice is both a verb and a noun in American (in British usage, practice is the noun and practise the verb).

Americans dispense with some silent letters in diphthongs,  and thus write anesthetic, maneuver, archeology, fetus, hemolysis rather than anaesthetic, manoeuvre, archaeology, foetus, haemolysis.

Americans sometimes write ax for axe, by for bye. 

Some Americans write focussed; others do not. The British always write focused.

Americans do not double the “l” as in traveler, traveling, fueled; the British do.

The man who discovered aluminum/aluminium   originally called it  alumium. A busybody reviewer said it should properly  be called  “aluminium”  to rhyme with sodium, calcium and magnesium, all discovered around the same time. Then again, some metals, like platinum and tantalum eschewed the -ium ending, and so do Americans.  So now we have two words for  one metal. 

American say period rather than full-stop. So that is what we use, period.