Company Writer's Guide
[For Illustration Only] B-7
Symbols for Units in General Use (Cont’d)
Unit Symbol Notes
darcy D 1 D = 1 cP (cm/s) (cm/atm) = 0.986 923 μm
2
A unit of permeability of a porous medium. By
traditional definition, a permeability of one
darcy will permit a flow of 1 cm
3
/s of fluid of 1
cP viscosity through an area of 1 cm
2
under a
pressure gradient of 1 atm/cm. For nonprecision
work 1 D may be taken equal to 1 μm
2
and 1 mD
equal to 0.001 μm
2
. Deprecated
(see ANSI Z210.1-1976).
day d
deci d SI prefix for 10
-1
.
decibel dB
degree (plane angle) . . . °
degree (temperature):
degree Celsius
°C
SI unit of Celsius temperature. The degree
Celsius is a special name for the kelvin, for use in
expressing Celsius temperatures or temperature
intervals.
degree Fahrenheit °F
Note that the symbols for °C, °F, and °R
comprise two elements, written with no space
between the ° and the letter that follows. The
two elements that make the complete symbol are
not to be separated.
degree Kelvin See kelvin.
degree Rankine °R
deka da SI prefix for 10.
dyne dyn Deprecated (see ANSI Z210.1-1976).
electronvolt eV
erg erg Deprecated (see ANSI Z210.1-1976).
