{"symbol":"m","name_singular":"meter","name_singular_aliases":"metre","definition":"The meter is the length of the path travelled by light in vacuum during a time interval of 1/299 792 458 of a second.","dimensionless":false,"source_xml":"base","unit_opts":["meter","metre","m"]}
{"symbol":"rad","name_singular":"radian","definition":"standard unit of angular measure, an angle that creates an arc in a circle equal in length to that circle's radius (roughly 57.3 degrees); as a ratio of two lengths, it has no dimension","comment":"SI derived unit","dimensionless":true,"source_xml":"derived","unit_opts":["radian","rad"]}
{"symbol":"°","name_singular":"arc_degree","name_singular_aliases":"angular_degree, degree, arcdeg","def":"(pi/180) rad","definition":"measurement of a plane angle representing 1/360 of a full rotation","dimensionless":false,"source_xml":"accepted","unit_opts":["arc_degree","angular_degree, degree, arcdeg","°"]}
{"symbol":"'","symbol_aliases":"′","name_singular":"arc_minute","name_singular_aliases":"angular_minute, arcminute, arcmin","def":"°/60","definition":"measurement of a plane angle equal to 1/60 arc degree","dimensionless":false,"source_xml":"accepted","unit_opts":["arc_minute","angular_minute, arcminute, arcmin","'","′"]}
{"symbol":"\"","symbol_aliases":"″","name_singular":"arc_second","name_singular_aliases":"angular_second, arcsecond, arcsec","def":"'/60","definition":"measurement of a plane angle equal to 1/60 arc minute","dimensionless":false,"source_xml":"accepted","unit_opts":["arc_second","angular_second, arcsecond, arcsec","\"","″"]}
{"symbol":"au","name_singular":"astronomical_unit","def":"1.49597870700e11 m","definition":"Exact definition according to 2012 resolution by the International Astronomical Union (IAU). Ostensibly equal to the mean distance from the center of the earth to the center of the sun.","comment":"According to resolution by the International Astronomical Union (IAU) in 2012 ","dimensionless":false,"source_xml":"accepted","unit_opts":["astronomical_unit","au"]}
{"symbol":"ua","name_singular":"astronomical_unit_BIPM_2006","def":"1.495979e11 m","definition":"unit of measurement equal to 149.6 million kilometers, the mean distance from the center of the earth to the center of the sun according to the International Bureau of Weights and Measures (BIPM) in 2006","comment":"Pre-2012 resolution by the IAU","dimensionless":false,"source_xml":"accepted","unit_opts":["astronomical_unit_BIPM_2006","ua"]}
{"name_singular":"nautical_mile","def":"1852 m","definition":"unit of distance at sea, set at 1852 meters (approximately one minute of arc measured along any meridian)","comment":"Unit is temporarily accepted for use with the SI.","dimensionless":false,"source_xml":"accepted","unit_opts":["nautical_mile"]}
{"symbol":"Å","symbol_aliases":"Å","name_singular":"angstrom","name_singular_aliases":"ångström","def":"1e-10 m","definition":"unit of length equal to one hundred-millionth of a centimeter (1 meter/10**10)","comment":"Unit is temporarily accepted for use with the SI.","dimensionless":false,"source_xml":"accepted","unit_opts":["angstrom","ångström","Å","Å"]}
{"name_singular":"fermi","def":"1e-15 m","definition":"unit of length equal to 10e-15 meters, a typical length-scale of nuclear physics","dimensionless":false,"source_xml":"common","unit_opts":["fermi"]}
{"name_singular":"light_year","def":"9.46073e15 m","definition":"unit of length equal to the distance traversed by light in one mean solar year (365.2422 days), a typical length-scale of astronomy","dimensionless":false,"source_xml":"common","unit_opts":["light_year"]}
{"name_singular":"micron","def":"1e-6 m","definition":"unit of length, a typical length-scale of technology and science fields","dimensionless":false,"source_xml":"common","unit_opts":["micron"]}
{"name_singular":"mil","def":"2.54e-5 m","definition":"unit of length equal to 0.001 inch, a typical length-scale for measuring wire diameters","dimensionless":false,"source_xml":"common","unit_opts":["mil"]}
{"name_singular":"parsec","def":"3.085678e16 m","definition":"unit of length corresponding to the distance at which the mean radius of the earth's orbit subtends an angle of one second of arc, a typical length-scale of astronomy","dimensionless":false,"source_xml":"common","unit_opts":["parsec"]}
{"name_singular":"printers_point","def":"3.514598e-4 m","definition":"unit of length equal to 1/72.27 inch, the original (standardized 1886) unit for measuring font size and other small items on a printed page (see also big_point)","dimensionless":false,"source_xml":"common","unit_opts":["printers_point"]}
{"name_singular":"chain","def":"2.011684e1 m","definition":"unit of length equal to 66 feet (4 poles), or 1/10 furlong, a typical (historical) scale of land surveying","dimensionless":false,"source_xml":"common","unit_opts":["chain"]}
{"name_singular":"printers_pica","name_singular_aliases":"pica","def":"12 printers_point","definition":"unit of length equal to 1/6 inch (12 printers points)","dimensionless":false,"source_xml":"common","unit_opts":["printers_pica","pica"]}
{"name_singular":"nmile","def":"nautical_mile","definition":"unit of length in the US Customary System, equal to 6,076 feet; typically used for air and sea navigation","dimensionless":false,"source_xml":"common","unit_opts":["nmile"]}
{"name_singular":"US_survey_foot","name_plural":"US_survey_feet","def":"(1200/3937) m","definition":"unit of length used for earlier survey data in some countries, slightly different than the current international foot","dimensionless":false,"source_xml":"common","unit_opts":["US_survey_foot","US_survey_feet"]}
{"name_singular":"US_survey_yard","def":"3 US_survey_feet","definition":"unit of length used in earlier survey data in some countries, slightly different than the current international yard","dimensionless":false,"source_xml":"common","unit_opts":["US_survey_yard"]}
{"name_singular":"US_survey_mile","name_singular_aliases":"US_statute_mile","def":"5280 US_survey_feet","definition":"unit of length used for earlier survey data in some countries, slightly slightly different than the current international mile","dimensionless":false,"source_xml":"common","unit_opts":["US_survey_mile","US_statute_mile"]}
{"name_singular":"rod","name_singular_aliases":"pole, perch","def":"16.5 US_survey_feet","definition":"unit of length equal to one-fourth of a surveyor's chain","dimensionless":false,"source_xml":"common","unit_opts":["rod","pole, perch"]}
{"name_singular":"furlong","def":"660 US_survey_feet","definition":"unit of length equal to 1/8 mile or 10 chains","dimensionless":false,"source_xml":"common","unit_opts":["furlong"]}
{"name_singular":"fathom","def":"6 US_survey_feet","definition":"unit of length equal to 6 feet in the imperial and US customary systems, typically used for measuring depth of water","dimensionless":false,"source_xml":"common","unit_opts":["fathom"]}
{"symbol":"in","name_singular":"international_inch","name_singular_aliases":"inch","def":"2.54 cm","definition":"unit of length equal to 25.4 mm by definition, used in imperial and US customary systems","dimensionless":false,"source_xml":"common","unit_opts":["international_inch","inch","in"]}
{"symbol":"ft","name_singular":"international_foot","name_singular_aliases":"foot","name_plural":"international_feet","name_plural_aliases":"feet","def":"12 international_inches","definition":"unit of length equal to 12 international inches, in the imperial and US customary systems; primarily used in the United States","dimensionless":false,"source_xml":"common","unit_opts":["international_foot","international_feet","foot","feet","ft"]}
{"symbol":"yd","name_singular":"international_yard","name_singular_aliases":"yard","def":"3 international_feet","definition":"unit of length equal to 3 international feet, in the imperial and US customary systems; primarily used in the United States","dimensionless":false,"source_xml":"common","unit_opts":["international_yard","yard","yd"]}
{"symbol":"mi","name_singular":"international_mile","name_singular_aliases":"mile","def":"5280 international_feet","definition":"unit of length equal to 5280 feet, equal to 12 international inches, in the imperial and US customary systems; primarily used in the United States and other smaller countries with ties to the US or United Kingdom","dimensionless":false,"source_xml":"common","unit_opts":["international_mile","mile","mi"]}
{"name_singular":"big_point","def":"inch/72","definition":"unit of length equal to 1/72 inch, standardized unit in modern computer-based publishing for measuring font size and other small items on a printed page (contrast to printers_point)","dimensionless":false,"source_xml":"common","unit_opts":["big_point"]}
{"name_singular":"barleycorn","def":"inch/3","definition":"unit of length based in medieval laws of England and Wales, defining an inch as being 3 barleycorns long (length of a corn of barley); still the basis for current shoe sizes in Great Britain and Ireland","dimensionless":false,"source_xml":"common","unit_opts":["barleycorn"]}
{"name_singular":"arpentlin","def":"191.835 foot","definition":"unit of length in French regions; a linear arpent is of length 10 perch (10 rod)","dimensionless":false,"source_xml":"common","unit_opts":["arpentlin"]}
{"symbol":"km","name_singular":"kilometer","name_singular_aliases":"kilometre","name_plural":"kilometers","name_plural_aliases":"kilometres","def":"1000 m","definition":"unit of length equal to 1000 meters","dimensionless":false,"unit_opts":["kilometer","kilometers","kilometre","kilometres","km"]}
{"symbol":"cm","name_singular":"centimeter","name_singular_aliases":"centimetre","name_plural":"centimeters","name_plural_aliases":"centimetres","def":"0.01 m","definition":"unit of length equal to 0.01 meter","dimensionless":false,"unit_opts":["centimeter","centimeters","centimetre","centimetres","cm"]}