A hair's breadth, or the width of human hair, is used as an informal unit of a very short length.[1] It connotes "a very small margin" or the narrowest degree in many contexts.[2][3][4][5][6][7]
Definitions
Look up by a hair's breadth in Wiktionary, the free dictionary.
This measurement is not precise because human hair varies in diameter, ranging anywhere from 17 μm to 181 μm [millionths of a metre][8] One nominal value often chosen is 75 μm,[5] but this – like other measures based upon such highly variable natural objects, including the barleycorn[9] – is subject to a fair degree of imprecision.[5][7]
Such measures can be found in many cultures. The English "hair's breadth"[6] 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").[10][11]
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).[12]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).[13][14]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.[15]
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."[16][17] 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."[18] Some German speakers similarly use “Muggeseggele,” literally “housefly’s scrotum,” as a small unit of measurement.[19]
^"By a nose". Free Dictionary. Retrieved December 30, 2016.
^"The meaning and origin of the expression: By the skin of your teeth". The phrase finder. Retrieved January 28, 2015.
^Sellner, Jan (9 March 2009). "Schönstes schwäbisches Wort: Großer Vorsprung für Schwabens kleinste Einheit". Stuttgarter Nachrichten (in German). Archived from the original on 27 September 2013. Retrieved 13 August 2013.
Sources
Boaz, James (1823-03-21). "On a fixed Unit of Measure". In Tilloch, Alexander; Taylor, Richard (eds.). Philosophical Magazine. Vol. 61. London: Richard Taylor. pp. 266–269.
Carey, Felix (1814). "Of Weights &c.". A grammar of the Burman language. Mission Press/Internet Archive. p. 209.
Crook, John; Osmaston, Henry (1994). "Weights and Measures". Himalayan Buddhist Villages. Delhi: Shri Jainendra Press. p. 133. ISBN 978-0-86292-386-0.
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.
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.