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Gram
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<p>The gram (originally gramme; <a href="/facts/SI/S7YLglNz">SI</a> unit symbol g) is a <a href="/facts/Physical_unit/pvTpWbmC">unit</a> of <a href="/facts/Mass/HHdc8XmF">mass</a> in the <a href="/facts/International_System_of_Units/S7YLglNz">International System of Units</a> (SI) equal to one thousandth of a <a href="/facts/Kilogram/lU2zbPk8">kilogram</a>. </p><p>Originally defined in 1795 as "the absolute <a href="/facts/Mass_versus_weight/gNvnevJE">weight</a> of a <a href="/facts/Volume/aeAXCBUd">volume</a> of pure <a href="/facts/Water/0lkXnJPK">water</a> equal to <a href="/facts/Cube_(algebra)/SqmlEEog">the cube</a> of the hundredth part of a <a href="/facts/Metre/hPhzc1CV">metre</a> [1 <a href="/facts/Cubic_centimetre/B8X0UHDI">cm3</a>], and at <a href="/facts/Melting_point_of_water/FFsl65l1">the temperature</a> of <a href="/facts/Melting_point/MY0w0h0k">melting</a> <a href="/facts/Ice/BGvkKFjD">ice</a>", the defining temperature (0 °C) was later changed to the temperature of <a href="/facts/Maximum_density/KqyY20a9">maximum density</a> of water (approximately 4 °C). Subsequent redefinitions agree with this original definition to within 30 <a href="/facts/Parts-per_notation/PozRuoLM">parts per million</a> (0.003%), with the maximum <a href="/facts/Density_of_water/FFsl65l1">density of water</a> remaining very close to 1 g/cm3, as shown by modern measurements. </p><p>By the late 19th century, there was an effort to make the <a href="/facts/Base_unit_(measurement)/7d7Uqd9N">base unit</a> the <a href="/facts/Kilogram/lU2zbPk8">kilogram</a> and the gram a derived unit. In 1960, the new <a href="/facts/International_System_of_Units/S7YLglNz">International System of Units</a> defined a <i>gram</i> as one thousandth of a kilogram (i.e., one gram is 1×10−3 kg). The kilogram, <a href="/facts/2019_revision_of_the_SI/g0h07jCX">as of 2019</a>, is defined by the <a href="/facts/International_Bureau_of_Weights_and_Measures/tPEu4X0s">International Bureau of Weights and Measures</a> from the metre, the second, and from the fixed numerical value of the <a href="/facts/Planck_constant/qGHAe3qq">Planck constant</a> (h). </p>