What metric unit is commonly used to measure liquids?

The liter is the commonly used metric unit for measuring liquids because it is part of the metric system, which is designed for scientific and everyday use across many countries. The liter (spelled 'litre' in some regions) is defined as the volume of a cube that measures 10 cm on each side, which equals 1,000 cubic centimeters. This unit provides a clear and standardized way to express liquid volumes, making it convenient for various applications, such as cooking, chemistry, and other scientific fields.

The other units mentioned, such as pint, gallon, and cup, are part of the imperial system, which is different from the metric system. While these units are widely used in certain countries, especially for everyday measurements in cooking and beverage servings, they do not fit within the framework of the metric system that relies on liters for liquid measurements. This distinction makes the liter the most appropriate choice for measuring liquids in a metric context.