∑=sigma is mainly used for summation, area density, transconductance, normal stress and conductivity.

φ = φ is mainly used for magnetic flux, electric flux, angle, lens power, heat flux, potential, diameter, empty set and Euler function.

φ = φ is mainly used for magnetic flux, electric flux, angle, lens power, heat flux, potential, diameter, empty set and Euler function.

δ = δ is mainly used for variation, enthalpy change, entropy change, diopter, discriminant and chemical shift in a quadratic equation.

η=eta is mainly used for hysteresis coefficient and mechanical efficiency.

θ=theta is mainly used for temperature and angle.

μ=mu is mainly used for permeability, microstructure, dynamic friction coefficient, hydrodynamic viscosity, monetary unit and Mobius function.

ω = ω is mainly used for ohm, angular velocity, angular frequency, electric angle of alternating current, mass fraction and unsaturation in chemistry.

Extended data:

Greek alphabet is a letter used in Greek, and it is also widely used in mathematics, physics, biology, chemistry, astronomy and other disciplines.

Greek letters are similar to English letters and Russian letters, but with different symbols and the same phonetic properties.

Greek letters are the earliest letters with vowels in the world.

Cyrillic letters and Georgian letters used in Russian and Ukrainian are all developed from Greek letters, so people who have studied Russian will feel deja vu when they use Greek letters.

Greek letters have entered the vocabulary of many languages. For example, the international word Delta comes from the Greek letter δ, because δ is a triangle.

References:

Baidu Encyclopedia _ Greek alphabet