Epsilon is (n-4), where n is the space-time dimension.
Epsilon stands for a small positive number.
Epsilon\varepsilon
Epsilon has no functional properties, but some upvalues are changed:
{Re[Epsilon] > -4, Re[Epsilon] > -3, Re[Epsilon] > -2, Re[Epsilon] > -1, Re[Epsilon] > 0}\{\text{True},\text{True},\text{True},\text{True},\text{True}\}