Guide for the Use of the International System of Units (SI)

10.1.2 Standardized mathematical signs and symbols 
 
As is the case for quantity symbols, most of the mathematical signs and symbols used in the physical 
sciences and technology are standardized. They may be found in Ref. [4: ISO 31-11] and should be used by 
NIST authors to the fullest possible extent.
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Examples:
^
(conjunction sign, p 
^
 q means p and q) 
≠
(a ≠ b, a is not equal to b) 
def
=
(
,
b
a
def
=
a
is by definition equal to b) 
≈ 
(a ≈ b, a is approximately equal to b) 
~
(a ~ b, a is proportionally equal to b) 
arcsin 
x
(arc sine of x) 
log
a 
x
(logarithm to the base a of x) 
lb 
x
(lb x = log
2 
x) 
ln 
x
(ln x = log
e 
x) 
lg 
x
 
(lg x = log
10 
x) 
10.2 Typefaces for symbols
 
Most word processing systems now in use at NIST are capable of producing lightface (that is, regular) or 
boldface letters of the Latin or Greek alphabets in both roman (upright) and italic (sloping) types. The 
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In addition to Refs. [4] and [5], quantity symbols can also be found in ANSI/IEEE Std 280-1985, IEEE Standard Letter Symbols for 
Quantities Used in Electrical Science and Electrical Engineering. Similarly, in addition to Ref. [4: ISO 31-11], mathematical signs and 
symbols are also given in ANSI/IEEE Std 260.3-1993, Mathematical Signs and Symbols for Use in Physical Sciences and 
Technology. Another publication is the book, Symbols, Units, Nomenclature and Fundamental Constants in Physics, 1987 Revision, 
by E. R. Cohen and P. Giacomo, International Union of Pure and Applied Physics, SUNAMCO Commission [reprinted from Physica, 
Vol. 146A, Nos. 1-2, p. 1 (November, 1987)]. See also Ref. [6], Note 3. 

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