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Name  Upper Case  Examples of Use  Lower Case  Examples of Use 

alpha  Α  α  Symbol for alpha radiation; An angle  
beta  Β  β  Symbol for beta radiation  
gamma  Γ  γ  Symbol for gamma radiation  
delta  Δ  A change; the Discriminant$({b}^{2}4ac)$ in quadratics.  δ  A small change 
epsilon  Ε  ε  On it's own the relative permittivity. With a zero subscript, ${\epsilon}_{0}$, it's the permittivity of free space  
zeta  Ζ  ζ  
eta  Η  η  
theta  Θ  θ  An angle  
iota  Ι  ι  
kappa  Κ  κ  
lambda  Λ  λ  Wavelength; Probability of decay in a given time frame 

mu  Μ    μ 
Coefficient of Fraction;
${10}^{6}$; symbol for the muon. 
nu  Ν  ν  
xi  Ξ    ξ  the universal set. 
omicron  Ο  ο  
pi  Π  Product of terms  π  Almost exclusively, use for the ratio of $\frac{\mathrm{circumference}}{\mathrm{diameter}}$; Pion 
rho  Ρ  ρ  Density; Resistivity 

sigma  Σ  Sum of terms  σ  Stress; Standard Deviation 
tau  Τ  τ  Symbol for the tauon  
upsilon  Υ  υ  
phi  Φ  Magnet Flux Linkage  φ  Magnetic Flux 
chi  Χ  χ  
psi  Ψ  ψ  
omega  Ω  Ohm, unit of electrical resistance  ω  Angular speed/frequency 