A mile is a unit of distance equal to 5,280 feet, or about 1.6 kilometers. When someone says they live three miles from school, they mean the distance between their house and school could be walked in about an hour, or driven in a few minutes.

The mile comes from ancient Rome, where soldiers measured distances by counting their steps. One thousand paces (a pace being two steps, left and right) made a milia passuum, or “thousand paces.” The Romans built roads throughout their empire and placed stone markers every mile to help travelers know how far they'd come.

Today, miles are used primarily in the United States and a few other countries, while most of the world uses kilometers. When you see a speed limit sign saying 55, that's 55 miles per hour. Runners often train by running specific distances in miles, and road races come in standard lengths like a 5K (about 3.1 miles) or a marathon (26.2 miles).

The phrase go the extra mile means to do more than required or expected. If you go the extra mile on a school project by adding illustrations, research beyond the assignment, or extra polish, you're putting in effort beyond what anyone asked for. This expression recognizes that pushing yourself further than necessary often leads to better results.