ε
Symbol  Format  Data 

ε  Code Point 
U+03B5 
TeX 
\epsilon 

SVG 
The (epsilon) symbol is used in math as a variable to represent error bounds. For example, in calculus, limits are formally defined using the (epsilondelta) definition^{[1]}.
The Greek small letter delta (δ) is used in math as a variable. It appears in calculus in epsilondelta notation.
The capital Greek letter (Ε).

(ε, δ) "epsilon delta" definitions of limitsGrant Sanderson (3Blue1Brown)