This classic word riddle asks: what has one letter, starts with E, and ends with E?
The answer is an envelope.
An envelope starts with the letter E and ends with the letter E. It can also contain one letter inside it.
The trick is that the word “letter” has two meanings. It can mean a character of the alphabet, or it can mean a written message sent through the mail. The riddle uses both meanings at the same time.
Once you stop thinking only about alphabet letters and picture something that can physically hold a written letter, the answer becomes clear. That double meaning is what makes the riddle memorable.
