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{{short description|Metric unit of area}}

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}}File:Comparison of units of area.png|thumb|Image comparing the hectare (the small blue area at lower left) to other units. The entire yellow square is one square milesquare mile The hectare ({{IPAc-en|ˈ|h|É›|k|t|ɛər|,_|-|t|ɑːr}}; SI symbol: ha) is a non-SI metric unit of area equal to a square with 100-metre sides (1 hm2), that is, 10,000 square meters (10,000 m2), and is primarily used in the measurement of land. There are 100 hectares in one square kilometre. An acre is about {{convert|1.000|acre|ha|disp=out|abbr=off}} and one hectare contains about {{convert|1.000|ha|acre|disp=out}}.File:St. Enda's GAA ground, Omagh - geograph.org.uk - 556880.jpg|thumb|St. Enda's GAA ground, in Omagh. The playing field used in Gaelic football and hurlinghurlingIn 1795, when the metric system was introduced, the are was defined as 100 square metres, or one square decametre, and the hectare ("hecto-" + "are") was thus 100 ares or {{frac|1|100}} km2 (10,000 square metres). When the metric system was further rationalised in 1960, resulting in the International System of Units ({{tooltip|2=in French: Système International d'Unités|SI}}), the are was not included as a recognised unit. The hectare, however, remains as a non-SI unit accepted for use with the SI and whose use is "expected to continue indefinitely". Though the dekare/decare daa (1,000 m2) and are (100 m2) are not officially "accepted for use", they are still used in some contexts.

Description

{{anchor|table-comparison-of-area-units}}{| class="wikitable" style="float:right; padding:0 0 2em 3em; margin: .56em 0 0 .8em;" style="text-align:right;"|1 ca|1 m2 style="text-align:right;"|1 a|100 m2 style="text-align:right;"|1 ha|10,000 m2 style="text-align:right;"|100 ha|1,000,000 m21 km2!colspan="2"|non-SI comparisons!non-SI||metric style="text-align:right;"|0.3861 sq mi|1 km2 style="text-align:right;"|2.471 acre|1 ha style="text-align:right;"|107,639 sq ft|1 ha style="text-align:right;"|1 sq mi|259.0 ha style="text-align:right;"|1 acre|0.4047 haFile:Trafalgar Square, London 2 - Jun 2009.jpg|right|thumb|Trafalgar SquareTrafalgar SquareThe hectare ({{IPAc-en|ˈ|h|É›|k|t|ɛər|,_|-|t|ɑː|r}}WEB,weblinkweblink" title="web.archive.org/web/20110101110815weblink">weblink dead, 1 January 2011, hectare, Oxford DictionariesNon-SI units mentioned in the SI#Units officially accepted for use with the SI>accepted for use with SI units.{{Citationyear=2006 title=The International System of Units (SI)access-date=13 February 2008}} Chapter 5. The name was coined in French, from the Latin .Oxford English Dictionary, 1st edition s.v. In practice the hectare is fully derived from the SI, being equivalent to a square hectometre. It is widely used throughout the world for the measurement of large areas of land,BIPM>TITLE=SI BROCHURE, TABLE 6ACCESS-DATE=17 NOVEMBER 2014land management>management, including law (deed), agriculture, forestry, and town planning throughout the European Union,HTTP://EUR-LEX.EUROPA.EU/LEXURISERV/LEXURISERV.DO?URI=CONSLEG:1980L0181:20090527:EN:PDF TITLE = COUNCIL DIRECTIVE 80/181/EEC OF 20 DECEMBER 1979 ON THE APPROXIMATION OF THE LAWS OF THE MEMBER STATES RELATING TO UNIT OF MEASUREMENT AND ON THE REPEAL OF DIRECTIVE 71/354/EEC ACCESS-DATE=29 JANUARY 2010, New Zealand and Australia (since 1970).WEB,weblink Commonwealth of Australia, Metric Conversion Act, 1970, 14 Aug 2020, WEB,weblink Metric Pioneer, Metric Pioneer, 2020, 14 Aug 2020, However, the United Kingdom,WEB,weblink WEB , WEB, MYA/01/008 Agriculture Sectore Review,weblink Working Paper No. 6 – Agroindustry in Myanmar,weblink" title="web.archive.org/web/20130515190933weblink">weblink 15 May 2013, dead, and to some extent Canada, use the acre instead of the hectare for measuring surface or land area.{{Citation needed|date=August 2010}}Some countries that underwent a general conversion from traditional measurements to metric measurements (e.g. Canada) required a resurvey when units of measure in legal descriptions relating to land were converted to metric units.{{Citation needed|date=February 2010}} Others, such as South Africa, published conversion factors which were to be used particularly "when preparing consolidation diagrams by compilation".WEB,weblink Instructions for the Conversions of Areas to Metric, Law Society of South Africa, November 2007, 21 January 2011, 20 March 2018,weblink dead, In many countries, metrification redefined or clarified existing measures in terms of metric units. The following legacy units of area have been redefined as being equal to one hectare:Britannica.com, unit of measurement, accessed 30 October 2009

• Jerib () in Iran
• Djerib () in TurkeyEB1911, Turkey, 27, Caillard, Vincent Henry Penalver, Gibb, Elias John Wilkinson, Elias John Wilkinson Gibb, 426–467; see page 442 second para, Two categories of rent, fixed and proportional, are payable to the state by mine-owners. The fixed rent is 10 piastres per jerib (about 10,000 square metres), to be paid whether the mine is worked or not.,
• Gongqing ({{zh|t=公頃|s=公顷|first=t|p=gōngqǐng}}) in China
• Manzana in Argentina
• Bunder in the Netherlands (until 1937)WEB,weblink Oppervlakte, Area, Eenheden, constanten en conversies [Units, constants and conversion], nl, Oscar van Vlijmen, 11 September 2006, 15 January 2011, 19 June 2021,weblink dead

, BOOK,weblink Allereerste Gronden der Cijferkunst, Jacob de Gelder, 's-Gravenhage and Amsterdam, nl, 1824, 156, de Gebroeders van Cleef, Introduction to Numeracy, 19 September 2012,

History

The metric system of measurement was first given a legal basis in 1795 by the French Revolutionary government. The law of 18 Germinal, Year III (7 April 1795) defined five units of measure:WEB,weblink La loi du 18 Germinal an 3 " la mesure [républicaine] de superficie pour les terrains, égale à un carré de dix mètres de côté », fr, The law of 18 Germanial year 3 "The [Republican] measure of land area equivalent to a ten-metre square", Le CIV (Centre d'Instruction de Vilgénis) â€“ Forum des Anciens, 2 March 2010,

• The (:metre) for length
• The are (100 m2) for area [of land]
• The stère (1 m3) for volume of stacked firewoodWEB,weblink Le stère, Tout sur les unités de mesure [All the units of measure], fr, Thierry Thomasset, Université de Technologie de Compiègne, 21 March 2011,weblink" title="web.archive.org/web/20110721011132weblink">weblink 21 July 2011, dead

,

• The (:litre) (1 dm3) for volumes of liquid
• The gram for mass

In 1960, when the metric system was updated as the International System of Units (SI), the are did not receive international recognition. The International Committee for Weights and Measures ({{tooltip|2=in French: Comité international des poids et mesures|CIPM}}) makes no mention of the are in the 2019 edition of the SI brochure, but classifies the hectare as a "Non-SI unit accepted for use with the International System of Units".WEB , In 1972, the European Economic Community (EEC) passed directive 71/354/EEC,WEB,weblink Council Directive of 18 October 1971 on the approximation of laws of the member states relating to units of measurement, (71/354/EEC), 7 February 2009, 25 April 2009,weblink" title="web.archive.org/web/20090425221644weblink">weblink dead, which catalogued the units of measure that might be used within the Community. The units that were catalogued replicated the recommendations of the CGPM, supplemented by a few other units including the are (and implicitly the hectare) whose use was limited to the measurement of land.

Unit family

(File:Hectare Diagram.svg|right|thumb|upright=1.35| Definition of a hectare and of an are)The names centiare, deciare, decare and hectare are derived by adding the standard metric prefixes to the original base unit of area, the are.

Decimilliare

The decimilliare (dma, sometimes seen in cadastre area evaluation of real estate plots) is {{frac|1|10,000}} are or one square decimetre.BOOK,weblink Robinson's Progressive Practical Arithmetic: Containing the Theory of Numbers in Connection with Concise Analytic and Synthetic Methods of Solution, and Designed as a Complete Text-book on this Science for Common Schools and Academies, Horatio Nelson, Robinson, Daniel W., Fish, Ivison, Blakeman, Taylor, 1858, 363, Such usage of a double prefix is non-standard. The decimilliare is roughly a four-inch-by-four-inch square.

Centiare

The centiare is one square metre.DICTIONARY,weblink centiare, 16 October 2019, Dictionary.com, Dictionary.com, LLC, DICTIONARY,weblink centiare, Collins Dictionary, Collins Publishers, 16 October 2019,

Deciare

The deciare (rarely used) is ten square metres.DICTIONARY,weblink deciare, 16 October 2019, Merriam Webster Dictionary, Merriam-Webster, Incorporated,

{{anchor|are}}Are

{{Redirect|Are (unit)|the English verb|To be (disambiguation){{!}}To Be}}The are ({{IPAc-en|ɑːr}}WEB,weblink are, Oxford Dictionariesdate=September 2022bot=medic}} or {{IPAc-enPUBLISHER=MACMILLANDICTIONARY.COM 10 m × 10 m}}), used for measuring land area. It was defined by older forms of the metric system, but is now outside the modern International System of Units (SI).HTTP://WWW.BIPM.ORG/EN/SI/SI_BROCHURE/>TITLE=SI BROCHURE (8TH EDITION)PUBLISHER=BIPM, It is still commonly used in speech to measure real estate, in particular in Indonesia, India, and in various European countries.In Russian and some other languages of the former Soviet Union, the are is called (: 'a hundred', i.e. 100 m2 or {{frac|1|100}} hectare). It is used to describe the size of suburban dacha or allotment garden plots or small city parks where the hectare would be too large. Many Russian dachas are 6 ares in size (in Russian, ).

Decare

The decare or dekare ({{IPAc-en|ˈ|d|ɛ|k|ɑːr|,_|-|ɛər}}) is derived from deca and are, and is equal to 10 ares or 1000 square metres. It is used in NorwayWEB,weblink Decrease in total grain yield, Grain and oil seeds, area and production, 2002, Statistics NorwayOttoman Empire>Ottoman areas of the Middle East and BulgariaWEB , as a measure of land area. Instead of the name "decare", the names of traditional land measures are usually used, redefined as one decare:

• in GreeceΛεξικό της κοινής Νεοελληνικής (Dictionary of Modern Greek), Ινστιτούτο Νεοελληνικών Σπουδών, Θεσσαλονίκη, 1998. {{ISBN|960-231-085-5}}
• in the Balkans, Israel, Palestine, Jordan, Lebanon, Syria, and TurkeyBOOK, El-Eini, Roza I.M., Mandated landscape: British imperial rule in Palestine, 1929–1948,weblink 5 May 2009, 2006, Routledge, 978-0-7146-5426-3, xxiii, Currency and Measures,weblink
• is used for decare in Norway, from the old measure of about the same area.

Conversions {| class"wikitable"

|+Metric and British imperial/United States customary comparisons!Unit name!Symbol!Multiple of preceding unit!Fraction of succeeding unit!SI equivalents!British imperial/United States customaryequivalents|centiareca|0.1 da{{valu=m2}}{{convertm2disp=out|lk=out}}|deciareda10 ca0.1 a{{valu=m2}}{{convertm2disp=out|lk=out}}|areaBS350:PART 1:1974 CONVERSION FACTORS AND TABLES PART 1. BASIS OF TABLES. CONVERSION FACTORS>DATE=1974PAGE=7, 10 da0.1 daa{{valu=m2}}{{convertm2disp=out|lk=out}}|decaredaa10 a0.1 ha{{valu=m2}}{{convertm2disp=out|lk=out}}|hectareha10 daa0.01 km2'''{{valu=m2}}''''''{{convertm2disp=out}}'''|square kilometre{{val|u=km2}}100 ha|'''{{valu=m2}}''''''{{convertm2disp=out|lk=out}}'''(File:Sq hectare acre.jpg|thumb|An acre shown inside a hectare for size comparison)The most commonly used units are in bold.One hectare is also equivalent to:

• 1 square hectometre
• 1.008 (Japan)
• 2.381 (Egypt)
• 6.25 (Thailand)
• 10 or (Middle East)BOOK,weblink registration, metrication malta., Encyclopaedia of scientific units, weights, and measures: their SI equivalences and origins, François Cardarelli, 97, Springer Verlag, London, Berlin and Heidelberg, 2003, 1-85233-682-X, 29 March 2011,
• 10 (Greece)
• 15 or 0.15 WEB,weblink Chinese Measurements â€“ Units of Area, On-line Chinese Tools, 24 December 2010,

Unicode

The Unicode character {{unichar|33CA|SQUARE ha}}, in the CJK Compatibility block, is intended for compatibility with pre-existing East Asian character codes.WEB, Unicode.org, CJK Compatibility block,weblink It is not intended for use in alphabetic contexts.

See also

• Conversion of units
• Hectometre
• Order of magnitude

References

{{Reflist|2}}

External links

{{commons}}{{EB1911 Poster|Acre (land measure)}}{{wiktionary|hectare}}

• weblink" title="web.archive.org/web/20141111155820weblink">Official SI website: Table 6. Non-SI units accepted for use with the International System of Units

{{SI units}}{{Use dmy dates|date=June 2016}}