Did you know English is one of the few languages where the first-person singular pronoun "I" is always capitalized? Or that it contains words that can mean two completely opposite things? Even something as simple as the days of the week reveals a difference: in many other languages, they are always written in lowercase. English is one of the most widely spoken languages in the world, but that doesn’t mean it is easy to explain. In fact, some of its strangest features might surprise even native speakers. From unusual grammar rules to words with surprising pasts, English is filled with quirks that make it unlike any other language. Here are 10 fascinating things that make English unique.