Metric measurements — also known as the International ... with a little rainbow wheel showing all the approved SI basic units — from meter and kilogram right on through second, kelvin, ampere ...

The carob seed which became the modern carats shows how ancient Greeks devised ingenious ways to ensure fairness in trade.

Other units are based on these basic units but have a prefix in front. The prefix tells you how much bigger or smaller the unit is: ...

There are many different imperial measurements for length, some are used more regularly than others. Just like in metric measures, the unit of measure you use depends on the size of the item.