It’s All Greek to Me

You know you’re an engineer when you recognize Greek letters on fraternities because you’ve seen them in your classes, not the other way around. When you get that deep into math and science, sometimes English just doesn’t cut it, but if the whole point was to increase the number of possible variables, why does each Greek letter stand for five different things? See below, with notes on which fields you’d commonly find each definition in.

Γ – gamma function (math), Poynting factor (thermodynamics)
Δ – change (math)
Θ – wavefunction (math, quantum mechanics)
Λ – deBroglie wavelength (thermodynamics)
Ξ – one of the thermodynamic ensembles (thermodynamics)
Π – product (math)
Σ – summation (math)
Φ – dissipation (heat and mass transfer, fluids)
Ψ – wavefunction (math, quantum mechanics)

Ω – domain of integration (math), angular velocity (general science), thermodynamic 

       ensemble (thermodynamics)

Not used (they look like their English counterparts): Α, Β, Ε, Ζ, Η, Ι, Κ, Μ, Ν, Ο, Ρ, Τ, Υ, Χ

Here's where things get real fun:
α – kinetic energy correction factor (fluids), angle (math), heat diffusivity (heat and mass
      transfer)
β – angle (math), coldness (=1/k_bT; thermodynamics)
γ – specific weight (general science), activity coefficient (heat and mass transfer,
      thermodynamics), heat capacity ratio (thermodynamics, chemistry)
δ – distance (general science), delta function (math), Kronecker delta (δ_ij) (fluids, heat and
      mass transfer, quantum mechanics)
ε – molar absorptivity (chemistry), electromotive force (physics), electron charge (also
      physics, general science), permittivity of free space (hey, look, physics again), strain
      (fluids), permutation tensor (ε_ijk) (math, fluids), energy (general science), effectiveness
      (thermodynamics)
ζ – dimensionless breakage time (fluids)
η – dynamic viscosity (fluids), efficiency (thermodynamics)
θ – angle (math, general science)
κ – bulk modulus (fluids)
λ – wavelength (physics, general science), eigenvalue (math), distance (general science),
      mean free path (thermodynamics)
μ – dynamic viscosity (fluids), growth rate (biology), coefficient of friction (physics), chemical
      potential (thermodynamics), moment (physics), shear modulus (fluids), reduced mass
      (chemistry)
ν – kinematic viscosity (fluids), frequency (thermodynamics), stoichiometric coefficient
      (chemistry), microstate (thermodynamics), frequency factor (chemistry)
ξ – extent of reaction (chemistry), complex function (math), mesh size (fluids),
      nondimensional length (probably fluids)
π – 3.1415926535897932384626 (life), Henry’s law coefficient (thermodynamics, chemistry),
      dimensionless group (ChemE)
ρ – density (general science), mass concentration (heat and mass transfer)
σ – surface tension (fluids), standard deviation (math), stress tensor (fluids), stress (fluids),
      particle diameter (chemistry, kinetics), symmetry number (kinetics), Steffan Boltzmann
      constant (heat and mass transfer), resistivity (physics)
τ – torque (fluids), time (general science), deviatoric stress (fluids)
φ – probability function (math), characteristic function (math), polar angle (math), volume
      fraction (general science), benzene group (chemistry), fugacity coefficient
      (thermodynamics)
χ – mole fraction (ChemE)
ψ – wavefunction (math, quantum mechanics)
ω – angular velocity (general science), degeneracy of microstates (thermodynamics)
Not used: ι (looks like i), ο (looks like o), υ (no idea what this is)

ε and σ win for most definitions off the top of my head (8 each), with μ coming in second with 7 and φ in third with 6. Totally not confusing at all.