American English (AmE) is the form of English used in the United States.
British English (BrE) is the form of English used in the United Kingdom and the rest of the British Isles. It includes all English dialects used within the British Isles.


Historical Background

The English language was first introduced to the Americas by British colonization, beginning in the late 16th century. Differences between the two include pronunciation, grammar, lexis, spelling, punctuation, idioms, formatting of dates and numbers, and so
on.


Differences in pronunciation :

Stress

1)French stress

For many loanwords from French where AmE has final-syllable stress, BrE stresses an earlier syllable. Such words include:

• BrE first-syllable stress: adult, ballet, bidet, brochure, Bernard
• BrE second-syllable stress: attaché

A few French words have other stress differences:

• AmE first-syllable, BrE last-syllable: cigarette, magazine
• AmE first-syllable, BrE second-syllable: exposé
• AmE second-syllable, BrE last-syllable: New Orleans

-ate

Most 2-syllable verbs ending -ate have first-syllable stress in AmE and second-syllable stress in BrE : rotate, translate, vibrate.



2)Miscellaneous stress

BrE	AmE	words with relevant syllable stressed in each dialect
1st	2nd	cannot, casein, Kathleen
2nd	1st	defense (sport), guru, mama, papa, Augustine
1st	3rd	partisan, carburet(t)or
3rd	1st	Margarine
2nd	3rd	Advertisement
3rd	2nd	Oregano