How To Write Hyphen Notation

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A benefit of the International Organisation of Units (SI) is that written technical information is effectively communicated, overcoming the variations of linguistic communication, including spelling and pronunciation. Values of quantities are expressed using Arabic symbols for numbers paired with a unit symbol, often with a prefix symbol that modifies unit magnitude. International SI mode and usage publications focus on written advice. Verbal pronunciation of SI terminology is purposefully not addressed in the BIPM SI Brochure (French is the primary language, English is secondary), NIST SP 330 (uses American English spelling), NIST SP 811 (uses American English spelling), or IEEE/ASTM SI 10.

NIST SP 811 provides an editorial checklist for reviewing manuscripts' conformity with the SI and the bones principles of physical quantities and units.

Spelling

NIST guides use American English language spelling practice in accordance with the United States Government Printing Function Style Manual , found in Webster's 3rd New International Lexicon . All units and prefixes should exist spelled as shown in this guide. Examples: meter, liter, and deka, Non metre, litre, and deca.

Plurals

Units: Names of units are made plural only when the numerical value that precedes them is more 1. Examples: 0.25 liter (quantity is less than ane) and 250 milliliters (quantity is more than one).
Symbols: Symbols for units are never pluralized. For instance, 250 mm = 250 millimeters, Non 250 mms.

Capitalization

Units: The names of all units get-go with a lower example letter except, of form, at the beginning of the judgement. There is i exception: in "degree Celsius" (symbol °C) the unit "degree" is lower case but the modifier "Celsius" is capitalized. Thus, body temperature is written equally 37 degrees Celsius.
Symbols: Unit symbols are written in lower instance letters except for liter and those units derived from the name of a person (m for meter, but W for watt, Pa for pascal, etc.).
Prefixes: Symbols of prefixes that mean a one thousand thousand or more are capitalized and those less than a 1000000 are lower case (M for mega (millions), 1000 for milli (thousandths)).

Spacing

A space is used between the number and the symbol to which it refers. For case: 7 g, 31.4 kg, 37 °C.

When a metric value is used as a 1-thought modifier before a substantive, hyphenating the quantity is not necessary. However, if a hyphen is used, write out the name of the metric quantity with the hyphen between the numeral and the quantity. For example:

a two-liter bottle, NOT a 2-L bottle;
a 100-meter relay, Not a 100-g relay;
35-millimeter film, NOT 35-mm film

Spaces are not used between prefixes and unit names nor betwixt prefix symbols and unit of measurement symbols. Examples: milligram, mg (NOT milli-gram or one thousand-yard); kilometer, km (NOT kilo-meter or k-one thousand); terahertz, THz (NOT tera-hertz or T-Hz).

Punctuation

DO NOT utilise a period with metric unit of measurement names and symbols except at the end of a sentence.

Decimal Point

The dot or period is used as the decimal signal within numbers. In numbers less than one, zero should exist written before the decimal point. Examples: 7.038 g; 0.038 g.

Prefixes

Some of the metric units listed higher up include prefixes such as kilo, centi, and milli. Prefixes, added to a unit name, create larger or smaller units by factors that are powers of x. For example, add the prefix kilo, which means a grand, to the unit of measurement gram to indicate 1000 grams; thus 1000 grams become 1 kilogram. Compound prefix names or symbols are not permitted. Example: nm (nanometer), Non mμm (millimicrometer).

For historical reasons, the proper noun "kilogram" for the SI base unit of mass contains the name "kilo," the SI prefix for 10³. Thus, because chemical compound prefixes are unacceptable, symbols for decimal multiples and submultiples of the unit of mass are formed by attaching SI prefix symbols to g (gram). The names of such multiples and submultiples are formed by attaching SI prefix names to the name "gram." Example: i mg, NOT 1 μkg (i microkilogram).

Incorrect Terms

The prefix "kilo" stands for ane thousand of the named unit. It is non a stand-alone term in the metric system. The most common misuse of this is the use of "kilo" for a "kilogram" of something. The word "micron" is an obsolete term for the quantity "micrometer." Also "degree centigrade" is no longer the correct unit of measurement term for temperature in the metric system; it has been replaced by caste Celsius. The proper name "metric ton" rather than "tonne."

Pronunciation

The pronunciation of common metric units is well known, except for pascal, which rhymes with rascal, and hectare, which rhymes with blank. The first syllable of every prefix is accented, not the second syllable. Instance: Kill-oh-meter, NOT kil-LOM-meter. Boosted pronunciation data is bachelor online.

Conversions

Conversions should follow a rule of reason: do non use more significant digits than justified by the precision of the original data. For example, 36 inches should be converted to 91 centimeters, not 91.44 centimeters (36 inches x 2.54 centimeters per inch = 91.44 centimeters), and twoscore.1 inches converts to 101.nine centimeters, not 101.854.

Time

The SI unit of time (really time interval) is the second (s) and should exist used in all technical calculations. When time relates to calendar cycles, the minute (min), hour (h), and twenty-four hours (d) might be necessary. For example, the kilometer per 60 minutes (km/h) is the usual unit for expressing vehicular speeds.

International Paper Sizes

The International System of Units (SI) is about measuring the weight or dimensions of objects, non changing their sizes. The U.Due south. paper industry uses several customary paper formats that all have metric dimensions. Whatsoever object weighed or measured using the SI has a metric size (e.thousand., a typical folio of office newspaper is 215 mm past 280 mm), just as the same object measured using customary units has a size (8.5 in past 11 in). While the standardization of sizes provides some benefits past simplifying things, the process of standardization is contained of the organisation of measurement.

Notation: This information is published as NIST LC 1137, Metric Style Guide for the News Media. To asking a difficult copy, please contact the Metric Plan.

For More Detail: Detailed metric information and precise conversions are bachelor in NIST SP 811 and SP 1038 PDF. SP 811 likewise provides an editorial checklist for reviewing manuscripts conformity with SI and the basic principles of concrete quantities and units. It is bachelor past calling the NIST Metric Programme at (301) 975-3690 or TheSI [at] nist.gov (email) .

Resources

Writing with the SI (January 2021). Increase familiarity with of SI writing conventions, add clarity to work correspondence and build confidence communicating measurement results.
SI/Metric Usage (US Metric Association). Listing highlights of import points to help with metric organisation communication, including common writing errors.
How Many? A Dictionary of Units of Measurement (Rowlett). Useful tips on using numbers and unit symbols in measurements.
Condign Familiar with SI.
Everyday Estimation.
Metrication FAQs.
SI Publications.
NEST-R (STEM Registry)
NIST Education Resource