A hair's breadth, or the width of human hair, is used as an informal unit of a very short length. It connotes "a very small margin" or the narrowest degree in many contexts.
Definitions
This measurement is not precise because human hair varies in diameter, ranging anywhere from 17 μm to 181 μm [millionths of a metre] One nominal value often chosen is 75 micrometres (0.0030 in), but this – like other measures based upon such highly variable natural objects, including the barleycorn – is subject to a fair degree of imprecision. Such measures can be found in many cultures. The English "hair's breadth" has a direct analogue in the formal Burmese system of Long Measure. A "tshan khyee", the smallest unit in the system, is literally a "hair's breadth". 10 "tshan khyee" form a "hnan" (a Sesamum seed), 60 (6 hnan) form a mooyau (a species of grain), and 240 (4 mooyau) form an "atheet" (literally, a "finger's breadth"). Some formal definitions even existed in English. In several systems of English Long Measure, a "hair's breadth" has a formal definition. Samuel Maunder's Treasury of Knowledge and Library of Reference, published in 1855, states that a "hair's breadth" is one 48th of an inch (and thus one 16th of a barleycorn). John Lindley's An introduction to botany, published in 1839, and William Withering' An Arrangement of British Plants, published in 1818, states that a "hair's breadth" is one 12th of a line, which is one 144th of an inch or ~176 μm (a line itself being one 12th of an inch). Carl Linnaeus had earlier recommended, in place of Joseph Pitton de Tournefort's geometric scale for botanical measurements, a scale starting with a "hair's breadth" (capillus) which was one 12th of a line (linea), one 6th of a (finger) nail (unguis), and likewise 144th of a thumb (pollex); which itself was equal to a (Parisian) inch.
Other body part measurements Winning a competition, such as a horse race, "by a whisker" (a short beard hair) is a narrower margin of victory than winning "by a nose." An even narrower anatomically-based margin might be described in the idiom "by the skin of my teeth," which is typically applied to a narrow escape from impending disaster. This is roughly analogous to the phrase "as small as the hairs on a gnat's bollock." Some German speakers similarly use “Muggeseggele,” literally “housefly’s scrotum,” as a small unit of measurement.
See also Beard-second List of humorous units of measurement List of unusual units of measurement Indefinite and fictitious numbers
References
Notes
Citations
Sources
Further reading Dalzell, Tom; Victor, Terry, eds. (2013). The New Partridge Dictionary of Slang and Unconventional English. Routledge, Taylor & Francis Group. p. 1843. ISBN 978-1-317-37252-3. Dickson, Paul (1994). War Slang: Fighting Words and Phrases of Americans from the Civil War to the Gulf War. Ann Arbor: University of Michigan Press. p. 286. ISBN 0-671-75022-4. Dickson, Paul (April 11, 2011). War Slang: American Fighting Words & Phrases Since the Civil War. Courier Corporation. p. 286. ISBN 978-0-486-47750-3. Dorson, Richard Mercer (1986). Handbook of American Folklore. Bloomington, Indiana: Indiana University Press. p. 123. ISBN 0-253-20373-2. Hales, John (2005). Shooting Polaris a personal survey in the American West. Columbia, Missouri: University of Missouri Press. p. 45. ISBN 0-8262-1616-1. Jillette, Pen (2004). Sock: A Novel. St. Martin's Publishing. p. 114. ISBN 1-4299-6131-7. Johnson, Sterling (1995). English as a Second f*cking Language. New York: Saint Martin's Press, St. Martin's Griffin. ISBN 978-0-312-14329-9. McYoung, Mark Animal (1991). Fists, Wits and a Wicked Right:Surviving on the Wild Side of the Street. Boulder, Colorado: Paladin Press. p. 25. Michaelis, David (1983). The best of friends: profiles of extraordinary friendships (Print). New York: Morrow. p. 231. ISBN 0-688-01558-1. Morton, Mark S. (2003). The lover's tongue a merry romp through the language of love and sex (Print). Toronto Ontario: Insomniac Press. p. 134. ISBN 1-894663-51-9. Partridge, Eric; Dalzell, Tom; Victor, Terry (2008). The Concise New Partridge Dictionary of Slang and Unconventional English (Print). London New York: Routledge. pp. 535, 1596 & 1601. ISBN 978-0-415-21259-5. Raudaskoski, Heikki (January 1997). "'The Feathery Rilke Mustaches and Porky Pig Tattoo on Stomach': High and Low Pressures in Gravity's Rainbow". Postmodern Culture. 7 (2). doi:10.1353/pmc.1997.0007. Retrieved January 20, 2015. Spelvin, Georgina (2008). The Devil Made Me Do It (Print). Los Angeles, California: Lulu.com, Little Red Hen Books. p. 110. ISBN 978-0-615-19907-8.
