Editing Inch (section)

{{Short description|Unit of length}}
{{Redirect|Inches||Inch (disambiguation)}}
{{use British English|date=August 2021}}
{{Use dmy dates|date=April 2022}}
{{Infobox unit
| image    = Inch tape.jpg
| caption  = A [[measuring tape]] with inches
| symbol   = in
| symbol2 = {{pprime}} (the [[double prime]])<ref name="Unicode-U2000">{{cite web |url=http://unicode.org/charts/PDF/U2000.pdf |title=The Unicode Standard 12.1 — General Punctuation ❰ Range: 2000—206F ❱ |author=Unicode Consortium |date=2019 |website=Unicode.org}}</ref>
| standard = [[Imperial units|Imperial]]/[[US customary units|US]] units
| quantity = [[Length]]
| units2   = [[Metric system|Metric]] ([[SI]]) units
| inunits2 = 25.4&nbsp;[[millimetre|mm]]
| units1   = Imperial/US units
| inunits1 = {{sfrac|36}}&nbsp;[[yard (unit)|yd]] or {{sfrac|12}}&nbsp;[[foot (unit)|ft]]
}}
[[File:3 inch zoll pipe.jpg|thumb|A fire hydrant marked as 3-inch]]

The '''inch''' (symbol: '''in''' or '''[[prime (symbol)|{{pprime}}]]''') is a [[Units of measurement|unit]] of [[length]] in the [[imperial units|British Imperial]] and the [[United States customary units|United States customary]] [[System of measurement|systems of measurement]]. It is equal to {{sfrac|1|36}} [[yard]] or {{sfrac|1|12}} of a [[foot (unit)|foot]]. Derived from the [[Uncia (unit)|Roman uncia]] ("twelfth"), the word ''inch'' is also sometimes used to translate similar units in other measurement systems, [[anthropic units|usually understood as deriving]] from the width of the human thumb.

Standards for the exact length of an inch have varied in the past, but since the adoption of the [[international yard]] during the 1950s and 1960s the inch has been based on the [[metric system]] and defined as exactly 25.4{{nbsp}}[[Millimetre|mm]].

{{anchor|Etymology}}