Vocabulary

Probably the major differences between British and American English lies in the choice of vocabulary. Some words mean different things in the two varieties for example:

Mean: American English - angry, bad humored, British English - not generous, tight fisted

Practice British & American with these exercises, 1, 2, 3, 4.
If in doubt, use this British to American vocabulary tool.

For more vocabulary practice, visit these sites:
Can you put the words used to talk about restaurants in the right spaces?
Can you put the rubbish in the correct recycle bin?