Symbols:E

Set

 * $E$

Used by some authors to denote a general set.

Identity Element

 * $e$

Used to indicate the identity element in a general algebraic structure.

If $e$ is the identity of the structure $\left({S, \circ}\right)$, then a subscript is often used: $e_S$.

This is particularly common when more than one structure is under discussion.

Euler's Number

 * $e$

Euler's number $e$ is the base of the natural logarithm $\ln$.

$e$ is defined to be the unique real number such that the value of the (real) exponential function $e^x$ has the same value as the slope of the tangent line to the graph of the function.

Experiment

 * $\mathcal E$

Expectation

 * $\expect X$

Conditional Expectation

 * $\expect {X \mid B}$