Let's look at "ε":

ε, the fifth letter of the Greek alphabet, uppercase ε, lowercase ε, and the Latin alphabet e is changed from ε. It can also refer to a phonetic symbol used in American English, that is, the e sound of bed. It is also the minimum energy value ε (called energy quantum) in the energy quantization hypothesis of German physicist Planck.

Physics: dielectric constant of conductor; It is also the minimum energy value ε (called energy quantum) in the energy quantization hypothesis of German physicist Planck.

The phonetic symbol used in American English is the e sound of bed.

In advanced mathematics, ε can be any given positive real number.

In the relationship of mathematical sets, the ∈ symbol indicating "belonging".

This is the symbol of levi-Civita.

Computer Science: Accuracy of Empty Strings and Numeric Patterns.

The Latin letter e is changed from Epsilon.

It often indicates the energy or electric potential energy of photons.