Editing Kilogram (section)

{{Short description|Metric unit of mass}}
{{Redirect|kg||KG (disambiguation){{!}}KG}}
{{Use dmy dates|date=October 2024}}
{{Infobox unit
| name          = kilogram
| image         = Poids fonte 5 kg à 2 hg 02.jpg
| caption       = A series of 5, 2, 1, 0.5 and 0.2 kilogram weights, made of [[cast iron]]
| standard      = [[SI]]
| quantity      = [[mass]]
| symbol        = kg
| units1        = [[Avoirdupois]]
| inunits1      = {{Ublist|≈ {{val|2.2046}} [[pound (mass)|pounds]]<ref group="Note">The avoirdupois pound is part of both [[United States customary units|United States customary system of units]] and the [[Imperial units|Imperial system of units]]. It is [[International yard and pound|defined as exactly]] {{val|0.45359237|u=kilograms}}.</ref>|≈ {{val|35.274|ul=oz}}}}
| units2        = British Gravitational
| inunits2      = ≈ {{val|0.0685}} [[slug (unit)|slugs]]
| units3        = [[CGS unit]]s
| inunits3      = {{val|1000|ul=g}}
| units4        = Daltons
| inunits4      = {{val|6.02214076|e=26|ul=Da}}
}}

The '''kilogram''' (also spelled '''kilogramme'''<ref name=":1" />) is the [[International System of Units#Base units|base unit]] of [[mass]] in the [[International System of Units]] (SI), equal to one thousand grams. It has the unit symbol '''kg'''.<ref name=":1" /> The word "kilogram" is formed from the combination of the [[metric prefix]] [[kilo-]] (meaning one thousand) and [[gram]];<ref>{{Cite web |title=Kilogram |url=https://www.collinsdictionary.com/dictionary/english/kilogram |access-date=14 October 2024 |website=Collins Online Dictionary}}</ref> it is colloquially [[Shortening (linguistics)|shortened]] to "'''kilo'''" (plural "kilos").<ref>[https://www.merriam-webster.com/dictionary/kilo Merriam-Mebster definition of Kilo]</ref>

The kilogram is an SI [[Base unit (measurement)|base unit]], defined ultimately in terms of three [[International System of Units#SI defining constants|defining constant]]s of the SI, namely [[Caesium standard|a specific transition frequency]] of the [[Isotopes of caesium|caesium-133]] atom, the [[speed of light]], and the [[Planck constant]].<ref name="SIBrochure9thEd"/>{{rp|131}}  A properly equipped [[metrology]] laboratory can calibrate a mass measurement instrument such as a [[Kibble balance]] as a primary standard for the kilogram mass.<ref>{{Cite web |date=July 7, 2021 |title=Mise en pratique for the definition of the kilogram in the SI |url=https://www.bipm.org/documents/20126/41489673/SI-App2-kilogram.pdf/5881b6b5-668d-5d2b-f12a-0ef8ca437176?version=1.9&t=1637237674882&download=false |access-date=February 18, 2022 |website=BIPM.org}}</ref>

The kilogram was originally defined in 1795 during the [[French Revolution]] as the mass of one [[litre]] of [[properties of water|water]]. The current definition of a kilogram agrees with this original definition to within 30 [[parts per million]]. In 1799, the platinum ''[[Grave (unit)#Kilogramme des Archives|Kilogramme des Archives]]'' replaced it as the standard of mass. In 1889, a cylinder composed of [[Platinum–iridium alloy|platinum–iridium]], the [[International Prototype of the Kilogram]] (IPK), became the standard of the unit of mass for the metric system and remained so for 130 years, before the current standard was [[2019 revision of the SI|adopted in 2019]].<ref name="vox" />