Proper Abbreviation of Measurement Units
Date: 03/04/2004 at 09:25:51 From: Norma Subject: Customary measurement abbreviations Is a period used after the abbreviations for the customary units of measurement? In the past, I understood that all abbreviations used a period. Now, I typically see inch as in., but ofter see foot (ft), yard (yd), and others with no period. I think maybe in. is used so as not to be confused with the word "in".
Date: 03/04/2004 at 12:21:40 From: Doctor Peterson Subject: Re: Customary measurement abbreviations Hi, Norma. As the following page points out, there is no "official" rule for writing customary units, as there is for SI (which omits all periods in unit symbols): Using Abbreviations or Symbols http://www.unc.edu/~rowlett/units/symbol.html That site chooses to follow SI rules for all units, so that no periods are used, even for "in". I found various writing style guides that recommend the rule you have observed, omitting the period except after "in.", presumably because of potential confusion. Here is one: ASAE Authors' Guide http://www.asae.org/pubs/style.html Omit periods after abbreviated units (except "in." for inch): 5 m, 30 cm, 40 ft This presumably results from familiarity with the metric system and its rules, which then spread to other units for the sake of consistency. Whether "in." will lose its period in common usage before the inch is fully replaced by the metric system is a good question! If you have any further questions, feel free to write back. - Doctor Peterson, The Math Forum http://mathforum.org/dr.math/
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