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A span is a unit of length based on the width of a human hand when the thumb and fingers are stretched apart, traditionally used in historical measurements. It matters because it represents one of humanity's earliest attempts to standardize measurements using the human body as a reference.
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Article
Some hand-based measurements, including the great span (4) A span is the distance measured by a human hand, from the tip of the thumb to the tip of the little finger. In ancient times, a span was considered to be half a cubit. Sometimes the distinction is made between the great span or full span (thumb to little finger) and little span or short span (thumb to index finger, or index finger to little finger).
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