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An italic lower-case e, the magnitude of the charge on a proton.
Also known as: Electron charge, Italic e
e is the elementary charge, exact since 2019. It is a different e from the mathematical constant 2.718…, from the electron as a particle, and from the exponent marker in scientific notation — one letter carrying four unrelated jobs.
Denotes the magnitude of the electric charge carried by a single proton, and the negative of that carried by an electron.
Contexts: Mathematics, Laboratory
Has had an exact value since 2019, which is how the ampere is now defined — by fixing this charge rather than by a force between wires.
Contexts: Mathematics, Laboratory
Shares its letter with at least three unrelated things in the same literature: Euler's number, the electron as a particle label, and the exponent marker in scientific notation. Which is meant is settled by context alone.
Contexts: Mathematics, Laboratory
A lower-case Latin letter e set in italic type, a closed upper bowl over an open lower curve.
The ampere is defined by fixing this charge.