Greek Small Letter Delta

U+03B4

\delta

The (delta) symbol is used in math as a variable. In calculus, the symbol used in epsilon-delta notation when defining the limit operator^[1].

Greek Capital Letter Delta | Symbol

The capital Greek letter Δ (Delta) is used in mathematics to represent the change in a variable.

1. (ε, δ) "epsilon delta" definitions of limits
   Grant Sanderson (3Blue1Brown)
   https://3blue1brown.com/lessons/epsilon-delta