90% of the time, speakers of English use just 7,500 words in speech and writing. These words appear in red, and are graded with stars. One-star words are frequent, two-star words are more frequent, and three-star words are the most frequent.
Differences between British and American English: subway
In the UK, a subway is an underground tunnel that people can walk through to get to the other side of a busy road: It's safest to use the subway to get from the car park to the museum. In the US, this is called an underpass. A subway in the US is an underground railway in a city: Take the subway to 14th Street.