This is courtesy of good old Wikipedia:

Greek letters are used in mathematics, science, engineering, and other areas where mathematical notation is used as symbols for constants, special functions, and also conventionally for variables representing certain quantities. In these contexts, the capital letters and the small letters represent distinct and unrelated entities. Those Greek letters which have the same form as Latin letters are usually not used: capital A, B, E, H, I, K, M, N, O, P, T, X, Y, Z; small o. Small ι (iota) and υ (upsilon) are also rarely used, since they closely resemble the Latin letters i and u. Sometimes font variants of Greek letters are used as distinct symbols in mathematics, in particular for phi and pi.

In mathematical finance, The Greeks are the variables denoted by Greek letters used to describe the risk of certain investments.

English-speaking mathematicians use neither the modern nor the historical Greek pronunciations of the names of the letters, but the traditional English pronunciation, e.g. [ˈθeɪtʌ] for θ cf. ancient [tʰɛ̂ːta] and modern [ˈθita].

[edit] Typography

The Greek letter forms used in mathematics are often different from those used in Greek-language text: they are designed to be used in isolation, not connected to other letters, and some use variant forms which are not normally used in current Greek typography.

The OpenType font format has the feature tag ‘mgrk’ “Mathematical Greek” to identify a glyph as representing a Greek letter to be used in mathematical (as opposed to Greek language) contexts.

The table below shows a comparison of Greek letters rendered in TeX and HTML. The font used in the TeX rendering is an italic style. This is inline with the convention that variables should be italicized. As Greek letters are more often than not used as variables in mathematical formulas, a Greek letter appearing similar to the TeX rendering is more likely to be encountered in works involving mathematics.

((But this table doesnt copy well to Answers = follow the link instead))

Greek Letters

Name TeX HTML Name TeX HTML Name TeX HTML Name TeX HTML Name TeX HTML

Alpha Αα Αα Digamma Ϝ Kappa Κκ Κκ Omicron Οο Upsilon Υυ Υυ

Beta Ββ Ββ Zeta Ζζ Ζζ Lambda Λλ Λλ Pi Ππ Ππ Phi Φφ Φφ

Gamma Γγ Γγ Eta Ηη Ηη Mu Μμ Μμ Rho Ρρ Ρρ Chi Χχ Χχ

Delta Δδ Δδ Theta Θθ Θθ Nu Νν Νν Sigma Σσ Σσ Psi Ψψ Ψψ

Epsilon Εε Εε Iota Ιι Ιι Xi Ξξ Ξξ Tau Ττ Ττ Omega Ωω Ωω

[edit] Concepts represented by a Greek letter

[edit] Αα (Alpha)

α represents:

the first angle in a triangle, opposite the side A.

one root of a quadratic equation, where β represents the other

the statistical significance of a result

the false positive rate in statistics

the reciprocal of the sacrifice ratio

the fine structure constant in physics

the angle of attack of an airplane

an alpha particle (He2+)

angular acceleration in physics

the linear thermal expansion coefficient

[edit] Ββ (Beta)

B represents the Beta function.

β represents:

the second angle in a triangle, opposite the side B.

one root of a quadratic equation, where α represents the other

the ratio of collector current to base current in a bipolar junction transistor (BJT) in electronics

the false negative rate in statistics

the beta coefficient, the non-diversifiable risk, of an asset in mathematical finance

the sideslip angle of an airplane

the first-order effects of variations in Coriolis force with latitude in planetary dynamics

a beta particle (e-)

sound intensity

[edit] Γγ (Gamma)

Γ represents:

the gamma function, a generalization of the factorial

the upper incomplete gamma function

the gamma distribution, a continuous probability distribution defined using the gamma function

the Christoffel symbols of the second kind

γ represents:

the lower incomplete gamma function

the third angle in a triangle, opposite the side C

the Euler-Mascheroni constant in mathematics.

second-order sensitivity to price in mathematical finance

a gamma ray

the heat capacity ratio in thermodynamics

the Lorentz factor in special relativity

[edit] Δδ (Delta)

Δ represents:

a finite difference

a difference operator

the Laplace operator

the angle that subtends the arc of a circular curve in surveying

δ represents:

a variation in the calculus of variations

the Kronecker delta function

the Dirac delta function

sensitivity to price in mathematical finance

[edit] Εε (Epsilon)

ε represents:

a small positive quantity; see limit

a random error in regression analysis

in set theory, the limit ordinal of the sequence .

in computer science, the empty string.

the Levi-Civita symbol.

in electromagnetics, dielectric permittivity.

emissivity

strain

set membership symbol ∈ is based on ε

[edit] Ϝ (Digamma)

Ϝ is sometimes used to represent the Digamma function, though the Latin letter F (which is nearly identical) is normally substituted.

[edit] Ζζ (Zeta)

ζ represents:

the Riemann zeta function and other zeta functions in mathematics

the coefficient of viscous friction in polymer dynamics

the damping ratio

relative vertical vorticity in fluid dynamics

[edit] Ηη (Eta)

η represents:

the partial regression coefficient in statistics.

elasticities in economics.

the absolute vertical vorticity (relative vertical vorticity + Coriolis effect) in fluid dynamics

an index of refraction

a type of meson

viscosity

efficiency

[edit] Θθ (Theta)

Θ represents:

an asymptotically tight bound related to Big O notation.

sensitivity to the passage of time in mathematical finance

θ represents:

a plane angle in geometry

the angle to the x axis in the xy-plane in spherical or cylindrical coordinates

potential temperature in thermodynamics

the mean time between failure in reliability engineering

soil water contents in soil science

Debye temperature

[edit] Ιι (Iota)

ι represents:

the index generator function in APL (in the form ⍳)

[edit] Κκ (Kappa)

κ represents:

the kappa curve

the condition number of a matrix in numerical analysis

curvature

dielectric constant (usually ε)

thermal conductivity (usually a lowercase Latin k)

a spring constant (usually a lowercase Latin k)

[edit] Λλ (Lambda)

Λ represents

the set of logical axioms in the axiomatic method of logical deduction in first-order logic

the cosmological constant

a type of baryon

λ represents

a unit of measure of volume equal to one microlitre (1 μL) or one cubic millimetre (1 mm³).

function expressions in the lambda calculus.

a general eigenvalue in linear algebra.

one wavelength in electromagnetic radiation, especially radio.

the arrival rate in queueing theory

the average life time or rate parameter in an exponential distribution (commonly used across statistics, physics, and engineering)

the failure rate in reliability engineering

the expected number of occurrences in a Poisson distribution in probability

the lagrange multiplier in the mathematical optimization method, known as the shadow price in economics

longitude in geodesy

linear density

[edit] Μμ (Mu)

μ represents:

the Möbius function in number theory

the population mean or expected value in probability and statistics

a measure in measure theory

micro, an SI prefix denoting 10-6 (one millionth)

the coefficient of friction in physics

the service rate in queueing theory

the dynamic viscosity in physics

magnetic permeability in electromagnetics

a muon

reduced mass

[edit] Νν (Nu)

ν represents:

frequency in physics in hertz (Hz)

Poisson’s ratio

a neutrino

[edit] Ξξ (Xi)

Ξ represents:

the grand canonical ensemble found in statistical mechanics.

a type of baryon

ξ represents:

a random variable.

the extent of a chemical reaction

coherence length

the damping coefficient

[edit] Οο (Omicron)

Ο represents:

big O notation (may be represented by an uppercase Latin O as well)

[edit] Ππ (Pi)

Π represents:

the product operator in mathematics.

a plane

π represents:

Archimedes’ constant, the ratio of a circle’s circumference to its diameter

the prime-counting function

profit in microeconomics and game theory

inflation in macroeconomics, expressed as a constant with respect to time

the state distribution of a Markov chain

a type of covalent bond in Chemistry (Pi bond)

a pion (pi meson)

ϖ (a graphic variant, see pomega) represents:

angular frequency of a wave, in fluid dynamics

longitude of pericenter in celestial mechanics

the comoving distance in cosmology

[edit] Ρρ (Rho)

ρ represents:

the radius in a polar coordinate system

the correlation coefficient in statistics

the sensitivity to interest rate in mathematical finance

density (mass per unit volume)

resistivity

the shape and reshape operators in APL (in the form ⍴)

[edit] Σσ (Sigma)

Σ represents:

the summation operator.

σ represents:

the divisor function in number theory

the population standard deviation or spread in probability and statistics

a type of covalent bond in Chemistry (sigma bond)

the selection operator in Relational algebra

stress

electrical conductivity

areal density

nuclear cross section

uncertainty

[edit] Ττ (Tau)

τ (lower-case) represents:

an interval of time

a mean lifetime

torque, the rotational force in mechanics.

the elementary tau lepton particle in particle physics.

the lifetime of a spontaneous emission process.

the time constant of any device, such as an RC circuit.

proper time in relativity.

a correlation coefficient — see Kendall’s tau.

the Golden ratio 1.618… (although φ (phi) is more common)

Ramanujan’s tau function in number theory.

tau in astronomy is a measure of opacity, or how much sunlight cannot penetrate the atmosphere.

tau in biochemistry is a protein associated to microtubules.

shear stress in continuum mechanics.

the number of divisors of highly composite numbers (sequence A000005 in OEIS)

the prefix of many stars, via the Bayer stellar designation system.

[edit] Υυ (Upsilon)

Y represents:

an elementary particle

[edit] Φφ (Phi)

Φ represents:

a wave function

magnetic flux

φ represents:

the golden ratio 1.618… in mathematics, art, and architecture

Euler’s totient function in number theory

the argument of a complex number in mathematics

the value of a plane angle in physics and mathematics

the angle to the z axis in spherical coordinates

latitude in geodesy

a wave function

electric potential

[edit] Χχ (Chi)

χ represents:

the chi distribution in statistics (X2 is the more frequently encountered chi-square distribution)

the chromatic number of a graph in graph theory

the Euler characteristic in algebraic topology

a variable in algebraic equations

electronegativity in the periodic table

the Rabi frequency

the Fourier transform of a linear response function (see susceptibility)

[edit] Ψψ (Psi)

Ψ represents:

Water potential

ψ represents:

the wave function in the Schrödinger equation of quantum mechanics

the stream function in fluid dynamics

yaw angle in vehicle dynamics

[edit] Ωω (Omega)

Ω represents:

the Omega constant

an asymptotic lower bound related to Big O notation

in probability theory and statistical mechanics, the set of possible distinct system states

the SI unit measure of electric resistance, the ohm

the rotation rate of an object, particularly a planet, in dynamics

a solid angle

a baryon

ω represents:

the first infinite ordinal

an asymptotically dominant quantity related to Big O notation

in probability theory, a possible outcome of an experiment

angular velocity / radian frequency

a complex cube root of unity – the other is ω2

vertical velocity in pressure-based coordinate systems (commonly used in atmospheric dynamics)

a meson

The symbol ϖ, a graphic variant of pi, is sometimes construed as omega with a bar over it; see Pi

RE:
I'm taking Physics and need to know Greek symbols and letters? Why?
Why do I need to know greek letters? Also, can anyone submit a list of the letters needed and their meaning?

http://musr.physics.ubc.ca/~jess/symbols/Greek.html

The web site I linked to DOES give you the information. Additionally – try physics greek symbols functions as your search string. I got THOUSANDS of hits. You couldn’t have looked that hard.