A unit of measurement is a standard quantity used to express and compare physical properties. Common examples include meter for length, kilogram for mass, and liter for volume. These units provide a consistent way to quantify and communicate measurements, making it easier to understand and share information. Units of measurement can be part of different systems, such as the metric system or the imperial system. The metric system is widely used around the world and is based on multiples of ten, while the imperial system is primarily used in the United States. Each system has its own set of units for various measurements.