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The measurement system that is used most frequently in the United States today. In the customary measurement system, short distance units were introduced based on the dimensions of the human body. For example, inch was used to represent the width of a thumb, and foot was used to represent the length of a human foot.
The advantage of introducing the customary measurement system this way is that it makes it easier to obtain a sense of the magnitude of these types of units. However, the drawback is the inconsistency of the units. One person´s feet are not likely to be equal to another´s. To improve the situation, nowadays, we actually use metric units to redefine the customary units. For example, 1 inch is defined as 2.54 cm. 1 foot is equal to 0.3048 m, and a yard equals exactly 0.9144 m.
