What is "e0"""?

As an AI language model, I assume you are referring to the mathematical constant "e", which is approximately equal to 2.71828.

The term "e0" is not commonly used or defined in mathematics or science. However, it is possible that it could represent the value of e raised to the power of zero, which is equal to one (e^0 = 1).

In physics, "e0" could refer to the electric permittivity of free space, which has a value of approximately 8.85418 x 10^-12 F/m.

Without further context, it is difficult to provide a more specific answer.