Hair's breadth

Human hair 2000X - SEM MUSE.tif

Hair's breadth is a term used to describe a very small distance or a very narrow margin. It originates from the width of a human hair, which is typically around 0.017 to 0.18 millimeters for scalp hair. The expression is often used metaphorically to signify something that is very close or that almost did not happen. For example, "He missed the target by a hair's breadth" implies that the miss was extremely slight.

Etymology

The term "hair's breadth" has been in use since at least the 16th century, reflecting the long-standing human practice of using the body as a source of measurement. The hair has been a particularly useful tool in this regard due to its uniform thickness and availability. Over time, "hair's breadth" has become synonymous with very small measurements in various fields, including precision engineering, art, and everyday language.

Usage in Measurement

In precision engineering and physics, a hair's breadth is not a standardized unit of measurement but serves as a colloquial reference to very small distances. When precision is required, measurements such as micrometers (μm) or nanometers (nm) are used instead. However, the term remains popular in informal contexts where exact measurements are not critical.

Metaphorical Use

Beyond its literal meaning, "hair's breadth" is widely used in a metaphorical sense to describe situations where a very small margin makes a significant difference. This can apply to time ("she arrived a hair's breadth away from being late"), distance, or even metaphorical space, such as decision-making or competitive scenarios.

Cultural References

The concept of a hair's breadth has permeated various cultures and literary works, often symbolizing the fine line between success and failure, life and death, or other dualities. It reflects the human fascination with narrow escapes and close calls.

See Also

• Measurement
• Human body
• Precision engineering