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.
The figure of Uncle Sam has been used, especially in the past, as a national symbol of the US. He is usually shown as a man with a white beard and a big hat, wearing clothes in the colours of the US flag. The expression comes from the abbreviation 'US'.