ec2-34-229-63-28.compute-1.amazonaws.com | ToothyWiki | StuartFraser | RecentChanges | Login | Advent calendar | Webcomic One of the recent topics of conversation amongst undergrad MatScis? has been quite how many different things certain letters in the Greek and Roman alphabets can actually mean, and the great potential for confusion this creates. As part procrastination and a minor part revision aid, I thought I'd create a list of possibilities for each letter, in uppercase and lower case. At somepoint I might add the greek letters, or alternatively someone else might; if I didn't actively want other people to help out I wouldn't have put it on a Wiki, would I?
Hebrew is possibly worthy of consideration. I know of at least Aleph and Bet from whatever my 4th year Set theory course was called - there are conceivably others. --CH
So, onwards. Due to the nature of the contributors this is heavily slanted towards cosmological and matierals science usage at the moment; this is an artefact and not an intention. I've ordered them by general broadness of utility, with a bias towards Materials terms because this page was originally intended as a revision aid for me after all.
Since a lot of people contribute to this page, and resolving conflicts is a pain, can I ask people to keep their edits at least five minutes apart? I've had six edit conflicts running now. Thanks. --SF
An obvious solution to running out of letters is to use more of them. I nominate Dr. Seuss' extension: [picture of them] --Pallando
Speed of light Heat capacity Constant of integration Crystal lattice parameter
d
Diameter Dipole moment Distance Derivative (as in dy/dx)
đ Imperfect differential (which depends on the path taken- e.g. thermodynamic quantities like đQ and đW)
e
The transcendental number which is the base of natural logarithms Electronic charge Coefficient of restitution
f
Frequency (also nu) Flux Farad (unit of capacitance) Function Probability density function (also phi)
g
Acceleration due to gravity Quantum degeneracy Gyromagnetic ratio Function (if f already used)
h
Planck's constant Miller Index Spatial distance, if x, y and z are in use (from 'height') Function (occasionally, if f and g already used)
ħ
Planck's Constant/2π
i
The square root of -1 Current density Miller Index in hexagonal 4-index notation Index for tensors
j
Particle flux of any kind (also J) Current density The square root of -1 Index for tensors
k
Boltzmann's constant "kilo-" (x10^3) prefix Wavevector Extinction coefficient Miller Index Quantum mechanical momentum Distance in reciprocal space Index for tensors The square root of -1 (rare) Many other empirical constants
l
Length Miller Index Index for tensors
m
Metres (unit of length) "milli-" prefix (x10^-3) Weibull modulus Mass (usually of a small body, say a satellite or planet) Apparent magnitude Mirror plane Nanotube chiral vector
n
Unknown integer value Number of atoms/moles of a substance Number density Refractive Index Polytropic index Nanotube chiral vector
o
'Shrinks to zero with', by contrast with O and Ω Not usable due to looking like a zero.
p
Probability Momentum Dipole moment vector Unknown prime value
Radius Position Product moment correlation coefficient
s
Displacement/Distance? Seconds (unit of time) Fibre aspect ratio in a composite Index into a matrix
t
Time Index into a matrix
u
Velocity before an event Lattice vector
v
Velocity Lattice vector
w
Lattice vector Second complex unknown or variable (if z already used) Fourth real unknown or variable value (if x, y, z already used) 4th-Dimension axis
x
Any real unknown or variable value Position Horizontal axis
y
Second real unknown or variable value (if x already used) Vertical axis
z
Any complex unknown or variable Third real unknown or variable value (if x, y already used) Depth axis
Uppercase
A
Area Amperes (unit of electrical current) Hamaker Constant Einstein A coefficient (atomic physics) Magnetic vector potential One of Oort's constants (Galactic dynamics) The AckermanFunctions Relative atomic mass
B
Magnetic Flux Density Binomial distribution Thickness (Fracture Mechanics) Einstein B coefficient (atomic physics) One of Oort's constants (Galactic dynamics)
C
Capacitance Concentration Coulombs (unit of charge) Set of complex numbers (written double-struck, ℂ) "Combination" binary operator (written <superscript-n>C<subscript-p>, for ways of choosing n objects from p, order-independant) Constant of integration Compliance
D
Diffusion coefficient Electric displacement (epsilon nought E + P) Covariant differentiation operator D/Dt?
E
Elastic Modulus (Young's Modulus) Energy Electric field Expectation E(X) of a random variable (also double-struck, 𝔼(X))
F
Force Free Energy (also G; depends on use of Gibbs or Helmholtz definitions) Faraday's Constant Face-centred lattice Cumulative probability density function (also capital phi)
G
Free Energy (also F; depends on use of Gibbs or Helmholtz definitions) Shear Modulus Universal gravitational constant "Giga-" prefix (x10^9) Electrical Conductance Bloch vector in hard condensed matter Einstein tensor
H
Enthalpy The H-field ( (one over mu nought) B + M) Entropy (in information theory I can't believe they'd actually use a letter which means something different in thermodynamics, but it is possible --SF) (IIRC) Heaviside function (zero from -infinity to 0, 1 from 0 to +infinity, integral of the Dirac δ function)
I
Current Intensity Moment of Inertia/Second? moment of Area Information (IIRC) Body-centred lattice Generic or unknown integral
It was almost an inevitability that I'd end up in a situation where the concept of "second moment of intensity" became relevant, wasn't it? --SF
J
Joules (unit of Energy) Particle Flux (also j) Total angular momentum Current, usually in 4D
K
Kelvin (unit of Temperature) Stress intensity factor Equilibrium Constant Constant of integration Adiabatic constant
L
Avogadro's Constant (also N) Orbital angular momentum Inductance
M
"Mega-" prefix (x10^6) Mass (usually of a large body, say a star) Magnetisation of a material Absolute magnitude
N
Newton (unit of force) Avogadro's Constant (also L) The set of natural numbers (written double-struck, ℕ) Neutron number (A-Z) Normal distribution
O
'Terms of order', as in O(x^2) By extension, 'grows at the same rate as'
P
Pressure Power (also W, allegedly) Polarisation of a material "Permutation" binary operator (written <superscript-n>P<subscript-p>, for ways of choosing n objects from p, order-important) Primitive lattice 4-momentum (special relativity) Probability of an event e.g. P(X = 0) (also ℙ(X = 0))
Q Charge Heat Flow rate Decay lifetime of a damped oscillation Set of rational numbers (written double-struck, ℚ)
R
Resistance Universal gas constant Set of real numbers Scale factor for the universe in general relativity Riemann curvature tensor Ricci Tensor Ricci Scalar
S
Entropy
T
Temperature Stress-Energy Tensor Kinetic Energy
U
Internal Energy 4-velocity
V
Volume Inverse square law field potential Volts (unit of Electrical potential)
W
Watts (unit of Power) Power (?someone justify this, please)I'm pretty sure I've seen it in textbooks, but can remove it if no one else agrees Do they? It strikes me as really odd because work is generally W and Power = d(Work)/dt Weight Work
X
A random variable (as in X is distributed normal 0,1) Hydrogen mass fraction (astronomy) Mole fraction (everyone else)
Y
A random variable (as in Y is distributed normal 0,1) Helium mass fraction
Z
Atomic number / Proton number Screened nuclear charge Set of integers (written double-struck, ℤ) Metallicity (anything other than H or He in astronomy!) Partition Function Normal distribution (random variable X ~ Z(0,1) ) A normal random variable Z ~ N(0,1)
Greek alphabet
Lowercase
α
Ferrite-like phase Angle between b and c vectors in a unit cell Fine structure constant Primary line of an X-Ray emission spectrum Helium-4 nucleus (α-particle) Shorthand for GMm Coherent state, as in a laser | α >
β
1/kT Free election (β-particle) Angle between a and c vectors in a unit cell
γ
Surface energy Austenite phase Lorentz factor Photon Shear angle Ratio of heat capacities at constant pressure over at constant volume Activity coefficient Angle between a and b vectors in a unit cell.
δ
Small quantity Crack tip opening displacement Dirac delta function (infinite at 0, 0 everywhere else) Kronecker delta δij (1 if i=j, 0 otherwise)
ε
Strain Dielectric constant Small quantity (less than γ) Energy density Interaction parameter Alternating tensor / Levi-Civita epsilon (εijk = 0 if any two of i,j,k are equal; =1 if i,j,k are an even permutation of (i,j,k); =-1 if an odd permutation)
ζ
Zeta potential (I think this one wins a "duh") Riemann's Zeta function (likewise)
η
Viscosity
θ
Often used for angles Temperature The polar angle in spherical polar co-ordinates
ι
Identity map (the map from a topological space X to itself, mapping every element to itself)
κ
Opacity Index for tensors in GR Thermal conduction coefficient
λ
Wavelength or other characteristic distance Mean free path Extensional viscosity Index for tensors in GR Parameter for defining lines in terms of vectors (as in x = a + λb)
μ
SI prefix "micro" (10^-6) Relative molecular/atomic mass Magnetic permeability Chemical potential Coefficient of friction Shear modulus (also G) Muon (A lepton charge -1 heavier than an electron). Charge carrier mobility Index for tensors in GR Parameter for defining planes in terms of vectors (as in x = a + λb + μc)
ν
Frequency Kinematic viscosity = η / ρ Neutrino Index for tensors in GR
ξ ο
π
The ratio between the circumference and diameter of a circle (for mathmos) 3.1415926..... (for physicists) 3 (for engineers) Of order unity (for Sanjoy) A measure of the likely future of the universe (for people doing general relativity with very long rulers) The pion or pi meson The prime counting function π(n)
ρ
Density Resistivity Index for tensors in GR
ς
σ
Stress (generally tensile or hydrostatic) Standard deviation Conductivity Stefan-Boltzmann constant Surface energy (also gamma) Surface coverage Cross-section of interaction.
τ
Characteristic timescale. Shear Stress Often used for a second time variable Tauon (a lepton charge -1, heavier than the electron and muon) Proper time in relativity (that is, time in a frame stationary and unaccelerated with respect to the clock)
υ φ
The Golden Ratio, (1+sqrt(5))/2 Used for angles (if θ is in use) The equatorial angle in spherical polar co-ordinates Probability density function (sometimes specifically the one for the Normal distribution)
χ Chi-square test Magnetic susceptibility (per site, if Χ is in use)
ψ
Wavefunction in quantum mechanics
ω
Angular Frequency Rotation tensor The infinity which is the number of natural numbers (also aleph_null) An event in Ω in probability/measure
Uppercase Α Β Γ
Continous function which has the same values as ! (factorial) for integers Affine connection (GR) Transition rate (QM)
Δ Change in value of a quantity.
Ε Ζ Η Θ Ι Κ Λ Cosmological Constant
Μ Ν Ξ Ο Π Product
Ρ Σ Sum
Τ Υ Upsilon particle in particle physics
Φ Cumulative probability density function (sometimes specifically the one for the Normal distribution) Gravitational Potential Magnetic Scalar potential Wavefunction, when Ψ is in use
Χ Magnetic Susceptibility
Ψ Wavefunction, especially in quantum mechanics
Ω Ohms (unit of resistance) Number of microstates corresponding to a single macrostate. Ratio of density of Universe to Critial density. Often subscripted for matter, radiation, dark energy, curvature,.... 'Grows faster than', as in y = Ω(x). Contrast with O and o. The event space in probability/measure