Unit of length

A unit of length is a way to measure how long something is. It's like measuring how many LEGO bricks you need to build a tower. There are many different units of length, just like there are different sizes of LEGO bricks. Some units of length are bigger, like meters, which are used to measure things like soccer fields or cars. Some units of length are smaller, like millimeters, which are used to measure things like the size of a bug or the thickness of a fingernail. When you want to measure how long something is, you pick a unit of length that makes sense for what you're trying to measure.