Quick Guide to Units and symbols

Remember to spell out the units in the text if not accompanied by a unit. Example: several inches vs. 23 cm.


Length (l)

m = meter(s)

cm = centimeter(s) (1 cm = 10-2 m)

mm = millmeter(s) (1 mm = 10-3 m)

μm = micrometer(s) (1 μm =10-6 m) NOT micron or μ

nm = nanometer(s) (1 nm = 10-9 m)

Å = angstrom(s) (1 Å = 10-10 m)

pm = picometer(s) (1 pm = 10-12 m)

in. = inch(es) (not recommended)

Volume (V)

L = liter(s)

mL = milliliter(s); cm3 = cubic centimeter(s)

Å3 = cubic angstrom(s)

Mass (m)

g = gram(s); kg = kilogram(s); mg = milligram(s); μg = microgram(s)

Density (D or ρ)

g/cm3 = gram(s) per cubic centimeter (please do not use Mg/m3)

Concentration (indicate with square brackets [ ] around chemical symbol, e.g., [Cl1-])

% = percent; ‰ = per mill

wt% = weight percent; mol% = mole percent; vol% = volume percent

M = molar concentration (1 M = 1 mol/L)

m = molal concentration (1 m = 1 mol/kg)

ppm = parts per million; ppb = parts per billion

Time (t)

s = second(s); min = minute(s); h = hour(s) Note: day(s), week(s), year(s) spelled out

Ma = million years; Ga = billion years (ago or date)

m.y. = million years; b.y. = billion years (duration)

Pressure (P)

Pa = pascal(s)

kPa = kilopascal(s); MPa = megapascal(s)

GPa = gigapascal(s)

bar or bars (no abbreviation)

kbar = kilobar(s)

atm = atmosphere(s) (not recommended)

Temperature (T)

K = Kelvin(s)

°C = degrees Celsius

Frequency (f or η)

Hz = hertz; kHz = kilohertz; MHz = megahertz

Energy

J = joule(s); kJ = kilojoule(s) (preferred)

cal = calorie(s); kcal = kilocalorie(s)

Miller indices--note that letter symbols are italicized but numberic values are not, e.g., [hkl] but [100]

hkl = diffraction symbol

(hkl) = face symbol

{hkl} = form symbol

[hkl] = edge or zone symbol

Unit-cell measurements

a, b, c = edge lengths; α, β, γ = angles

a, b, c = vectors--note boldface

Optical measurements:

    dispersion (r, v),
    optic axial angle (2V, 2Vx, 2Vz);
    principal vibration directions (E, O; X, Y, Z);
    refractive indices (n; nε, nω, nα, nβ, nγ where the n's are italic and the greek characters are subscripts)

Other abbreviations (roman type); cf. = compare; e.g. = for example; et al. = and others; etc. = and other things; i.e. = that is; p. = page(s); vs. = versus.

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