Symbols:Greek/Epsilon/Arbitrarily Small Positive Quantity

Arbitrarily Small Strictly Positive Real Number

Many a proof in analysis will famously start:

"Let $\epsilon > 0$ ..."

where it is frequently left unstated that $\epsilon$ is a real number, arbitrarily small.

The $\LaTeX$ code for $\epsilon > 0$ is \epsilon > 0 .

While $\epsilon$ is common, so is $\varepsilon$.

The symbols are, in general, interchangeable.

Some writers prefer $\epsilon$ and some prefer $\varepsilon$.

The $\LaTeX$ code for $\varepsilon$ is \varepsilon .

On $\mathsf{Pr} \infty \mathsf{fWiki}$ the preferred symbol is $\epsilon$.