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: gas
In the UK, gas usually refers to a clear substance like air that is burned to cook food or to heat your house: a gas boiler. Gas can also have this meaning in the US, but when American speakers say gas they are usually referring to a type of liquid fuel that is used to produce power in cars: We'd better get gas on our way out of town. In the UK, you call this fuel petrol.