[U.S. Government Printing Office Style Manual]
[Chapter 10 - Signs and symbols]
[From the U.S. Government Publishing Office, www.gpo.gov]


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                         10. SIGNS AND SYMBOLS

  10.1. The increased use of signs and symbols and their 
importance in technical and scientific work have emphasized the 
necessity of standardization on a national basis and of the 
consistent use of the standard forms.

  10.2. Certain symbols are standardized--number symbols (the 
digits, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9); letter symbols (the 
letters of the alphabet, a, b, c, d, etc.); and graphic symbols 
(the mathematical signs +, -, ,  x , ).

  10.3. The signs +, -, ,  x , and , etc., 
are closed against accompanying figures and symbols. When the 
x  is used to indicate ``crossed with'' (in plant or animal 
breeding) or magnification, it will be separated from the 
accompanying words by a space.

i-vii+1-288 pages
The equation A+B
The result is 4 x 4
20,0005,000
Early June  x  Bright (crossed with)
 x  4 (magnification)
  
  

Symbols with figures

  10.4. In technical publications the degree mark is used in 
lieu of the word degree following a figure denoting 
measurement.
  10.5. Following a figure, the spelled form is preferred. The 
percent symbol is used in areas where space will not allow the 
word percent to be used.

      In that period the price rose 12, 15, and 19 percent.
  not In that period the price rose 12 percent, 15 percent, and 
        19 percent.

  10.6. Any symbol set close up to figures, such as the degree 
mark, dollar mark, or cent mark, is used before or after each 
figure in a group or series.

$5 to $8 price range
5'-7' long, not 5-7' long
3 cents to 5 cents (no spaces)
2 to 7; 2 deg.1 deg.

but
Sec. 12 (thin space)
from 15 to 25 percent
45 to 65  deg.F not 45 deg. to 65 deg. F

Letter symbols

  10.7. Letter symbols are set in italic (see rule 10.8) or in 
roman (see rule 9.56) without periods and are capitalized only 
if so shown in copy, since the capitalized form may have an 
entirely different meaning.

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Equations

  10.8. In mathematical equations, use italic for all letter 
symbols--capitals, lowercase, small capitals, and superiors and 
inferiors (exponents and subscripts); use roman for figures, 
including superiors and inferiors.

  10.9. If an equation or a mathematical expression needs to be 
divided, break before +, -, =, etc. However, the equal sign is 
to clear on the left of other beginning mathematical signs.

  10.10.  A short equation in text should not be broken at the 
end of a line. Space out the line so that the equation will 
begin on the next line; or better, center the equation on a 
line by itself.

  10.11. An equation too long for one line is set flush left, 
the second half of the equation is set flush right, and the two 
parts are balanced as nearly as possible.

  10.12. Two or more equations in a series are aligned on the 
equal signs and centered on the longest equation in the group.

  10.13. Connecting words of explanation, such as hence, 
therefore, and similarly, are set flush left either on the same 
line with the equation or on a separate line.

  10.14. Parentheses, braces, brackets, integral signs, and 
summation signs should be of the same height as the 
mathematical expressions they include.

  10.15. Inferiors precede superiors if they appear together; 
but if either inferior or superior is too long, the two are 
aligned on the left.

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Chemical symbols

  10.16. The names and symbols listed below are approved by the 
International Union of Pure and Applied Chemistry. They are set 
in roman without periods.

----------------------------------------------------------------------------------------------------------------
                                            Atomic                                           Atomic
            Element                Symbol             Atomic         Element        Symbol              Atomic
                                            number  weight\1\                                number   weight\1\
----------------------------------------------------------------------------------------------------------------
Actinium.......................  Ac             89  227.0278   Mercury...........  Hg            80    200.59
Aluminum.......................  Al             13  26.98154   Molybdenum........  Mo            42     95.94
Americium......................  Am             95     (243)   Neodymium.........  Nd            60    144.24
Antimony.......................  Sb             51    121.75   Neon..............  Ne            10     20.179
Argon..........................  Ar             18    39.948   Neptunium.........  Np            93    237.0482
Arsenic........................  As             33   74.9216   Nickel............  Ni            28     58.69
Astatine.......................  At             85     (210)   Niobium...........  Nb            41     92.9064
Barium.........................  Ba             56    137.33   Nitrogen..........  N              7     14.0067
Berkelium......................  Bk             97     (247)   Nobelium..........  No           102  (259)
Beryllium......................  Be              4   9.01218   Osmium............  Os            76    190.2
Bismuth........................  Bi             83  208.9804   Oxygen............  O              8     15.9994
Bohrium........................  Bh            107   (262.0)   Palladium.........  Pd            46    106.42
Boron..........................  B               5     10.81   Phosphorus........  P             15     30.97376
Bromine........................  Br             35    79.904   Platinum..........  Pt            78    195.08
Cadmium........................  Cd             48    112.41   Plutonium.........  Pu            94  (244)
Calcium........................  Ca             20     40.08   Polonium..........  Po            84  (209)
Californium....................  Cf             98     (251)   Potassium.........  K             19     39.0983
Carbon.........................  C               6    12.011   Praseodymium......  Pr            59    140.9077
Cerium.........................  Ce             58    140.12   Promethium........  Pm            61  (145)
Cesium.........................  Cs             55  132.9054   Protactinium......  Pa            91    231.0359
Chlorine.......................  Cl             17    35.453   Radium............  Ra            88    226.0254
Chromium.......................  Cr             24    51.996   Radon.............  Rn            86  (222)
Cobalt.........................  Co             27   58.9332   Rhenium...........  Re            75    186.207
Copper.........................  Cu             29    63.546   Rhodium...........  Rh            45    102.9055
Curium.........................  Cm             96     (247)   Rubidium..........  Rb            37     85.4678
Dubnium........................  Db            105   (262.0)   Ruthenium.........  Ru            44    101.07
Dysprosium.....................  Dy             66    162.50   Rutherfordium.....  Rf           104   (261.0)
Einsteinium....................  Es             99     (252)   Samarium..........  Sm            62    150.36
Erbium.........................  Er             68    167.26   Scandium..........  Sc            21     44.9559
Europium.......................  Eu             63    151.96   Seaborgium........  Sg           106   (263.0)
Fermium........................  Fm            100     (257)   Selenium..........  Se            34     78.96
Fluorine.......................  F               9  18.998403  Silicon...........  Si            14     28.0855
Francium.......................  Fr             87     (223)   Silver............  Ag            47    107.8682
Gadolinium.....................  Gd             64    157.25   Sodium............  Na            11     22.98977
Gallium........................  Ga             31     69.72   Strontium.........  Sr            38     87.62
Germanium......................  Ge             32     72.59   Sulfur............  S             16     32.06
Gold...........................  Au             79  196.9665   Tantalum..........  Ta            73    180.9479
Hafnium........................  Hf             72    178.49   Technetium........  Tc            43   (98)
Hassium........................  Hs            108   (265.0)   Tellurium.........  Te            52    127.60
Helium.........................  He              2   4.00260   Terbium...........  Tb            65    158.9254
Holmium........................  Ho             67  164.9304   Thallium..........  Tl            81    204.383
Hydrogen.......................  H               1   1.00794   Thorium...........  Th            90    232.0381
Indium.........................  In             49    114.82   Thulium...........  Tm            69    168.9342
Iodine.........................  I              53  126.9045   Tin...............  Sn            50    118.69
Iridium........................  Ir             77    192.22   Titanium..........  Ti            22     47.88
Iron...........................  Fe             26    55.847   Tungsten..........  W             74    183.85
Krypton........................  Kr             36     83.80   Ununnilium........  Uun          110   (269.0)
Lanthanum......................  La             57  138.9055   Unununium.........  Uuu          111   (272.0)
Lawrencium.....................  Lr            103     (260)   Ununbium..........  Uub          112   (277.0)
Lead...........................  Pb             82     207.2   Uranium...........  U             92    238.0289
Lithium........................  Li              3     6.941   Vanadium..........  V             23     50.9415
Lutetium.......................  Lu             71   174.967   Xenon.............  Xe            54    131.29
Magnesium......................  Mg             12    24.305   Ytterbium.........  Yb            70    173.04
Manganese......................  Mn             25   54.9380   Yttrium...........  Y             39     88.9059
Meitnerium.....................  Mt            109   (266.0)   Zinc..............  Zn            30     65.38
Mendelevium....................  Md            101     (258)   Zirconium.........  Zr            40     91.22
----------------------------------------------------------------------------------------------------------------
\1\The atomic weights of many elements are not invariant but depend on the origin and treatment of the material.
  The values of atomic weight given here apply to elements as they exist naturally on Earth and to certain
  artificial elements. Values in parentheses are used for radioactive elements whose atomic weights cannot be
  quoted precisely without knowledge of the origin of the elements. The value given is the atomic mass number of
  the isotope of that element of longest known half life.


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Standardized symbols

  10.17. Symbols duly standardized by any national scientific, 
professional, or technical group are accepted as preferred 
forms within the field of the group. The issuing office 
desiring or requiring the use of such standardized symbols 
should see that copy is prepared accordingly.

Signs and symbols

  10.18. The following list contains some signs and symbols 
frequently used in printing. The forms and style of many 
symbols vary with the method of reproduction employed. It is 
important that editors and writers clearly identify signs and 
symbols when they appear within a manuscript.

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