Final answer:
A standard is a level of quality or performance accepted as normal, and in measurements, it refers to a commonly used unit for comparing physical quantities. The customary system includes feet, inches, and pounds, while the metric system uses meters, kilograms, and liters.
Step-by-step explanation:
A standard is a level of quality or performance that people accept as normal. In the context of measurements, a standard unit is one that is most commonly used for expressing and comparing the measurement of physical quantities. Both the customary and metric systems of measurement include standard units for weight (or mass), length, and liquid volume. For example, the customary system, which is commonly used in the United States, includes units such as feet, inches, pounds, cups, and gallons. In contrast, the metric system includes units like meters, kilograms, and liters.
It's important to understand that units are standards for expressing and comparing the measurement of physical quantities and can be expressed as combinations of four fundamental units. When we measure the weight, height, length, or size of something, we are using measurement units. These units serve as a reference that enables consistent communication of quantity across different regions and cultures.