What begins with an E and only contains one letter?

Here's a clever bit of wordplay that hinges on understanding the dual meaning of a common term. The item in question is a familiar stationery product, designed to protect and transport written communication. Its name starts with the fifth letter of the alphabet, and its primary function is to hold a single piece of correspondence, often referred to by the very word that completes the riddle's description.

This ingenious riddle plays on the fact that while the object itself is a container, it typically holds what we call "a letter"—a written message. Historically, envelopes, or covers for letters, have existed in various forms for millennia. Ancient civilizations used clay envelopes to protect important documents, while later, paper envelopes became common as postal systems developed. Their evolution reflects a continuous need for privacy and security in transmitting personal and official messages across distances.

Today, though digital communication has reduced their everyday use, envelopes remain essential for formal documents, greeting cards, and secure mail. They serve as a physical barrier, ensuring the contents arrive safely and confidentially. The simple act of sealing an envelope around a single written communication perfectly illustrates why this everyday item perfectly fits the description of something that begins with an E and indeed, only contains one letter.