Even though the words accent and dialect are often used interchangeably, they actually mean two different things. An accent refers to pronunciation. A dialect refers to pronunciation and vocabulary, grammar, and idiomatic phrases. Think of it this way, the Midwestern preference for the vowel sound ‘a’ as in ‘bad’, the New York City penchant to change the ‘er’ sound to ‘oi’ (as in Murphy to Moify), and the West Virginian fondness for dropping the ‘i’ sound in Ryan, so that it sounds like Ron, are all examples of regional accents.
Dialect, on the other hand, refers to the Midwestern word ‘pop’ as a kind of soft-drink, the New York ‘soda’ for its counterpart, and the Southern ‘coke’ for its equivalent… regardless if the said ‘coke’ is Sprite, 7-Up, or Pepsi. (View a map of this phenomena)
In addition to regions within the US, there are many words that are quite different between the English spoken on either side of the Atlantic. Why is this? One reason is that the newcomers to the Americas had to literally invent words to describe their new surroundings. One way they did this was to take two known English words and combine them to create a new word. Examples include ‘sagebrush’ and ‘rattlesnake’, typical enough to frontiersmen and women but not your everyday motif in Lancashire. Another way to expand the region’s repertoire of words was to ‘borrow’ them from speakers native to the area, like the words ‘canoe’ and ‘tobacco’. Eventually these words made it into the mainstream of ‘Americanisms’.
It’s estimated there are over 4,500 words used in American English that either don’t “exist” in British English or are used in an altogether different sense. The word ‘crib’, for example, is uniquely American; the word ‘cot’ is the British equivalent.
This begs the question… with different accents, and thousands of different words, are British and American English the same language or are they really two distinct dialects?