Elementary charge symbol

An italic lower-case e, the magnitude of the charge on a proton.

Also known as: Electron charge, Italic e

ScientificMathematicalStandard profile

Meanings

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.

Common modern usageVerified fact
Denotes the magnitude of the electric charge carried by a single proton, and the negative of that carried by an electron.
Contexts: Mathematics, Laboratory
Officially standardisedVerified fact
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
Common modern usageVerified fact
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

Visual description

A lower-case Latin letter e set in italic type, a closed upper bowl over an open lower curve.

Symmetry: none
Orientation: upright

Used alongside: Ampere symbol
The ampere is defined by fixing this charge.

Confidence

IdentityHigh confidence: High confidence because the identity is defined by a current official standard, but multiple independent sources agree.
Historical originModerate confidence: Moderate confidence because the historical origin is documented in encyclopedic references, but multiple independent sources agree, but early or supporting evidence is limited, but the regional or cultural match to this specific claim is not precise.
Current useHigh confidence: High confidence because the current use is defined by a current official standard, but multiple independent sources agree.
Visual matchHigh confidence: High confidence because the visual match is documented in encyclopedic references, but multiple independent sources agree.

Sources

ISO 80000, Quantities and units — recommended symbols
International Organization for Standardization · retrieved 2026-08-01
Paywalled and NOT READ. Registered so records can note that a recommended notation exists. It is widely departed from in practice, and no record types a meaning `official` on its basis. See docs/paywalled-standards.md.
The SI defining constants
Bureau International des Poids et Mesures · retrieved 2026-08-01
The seven constants whose exact values define the SI since 2019. Cited for the fact that a constant's value is fixed by definition rather than measured — a claim about the unit system, not about the notation.
Elementary charge
Wikipedia · retrieved 2026-08-01
Tertiary reference. Used for what a symbol denotes in ordinary scientific practice and for which fields reuse it, never for a claim that any body assigns the letter its meaning.
CODATA Internationally Recommended Values of the Fundamental Physical Constants
NIST / CODATA Task Group on Fundamental Constants · retrieved 2026-08-01
Authoritative for the recommended value and uncertainty of a physical constant, and for whether that value is exact by definition or measured. It fixes values; it does not decide which letter denotes which quantity, and no record cites it for a symbol's meaning.
Physical constant
Wikipedia · retrieved 2026-08-01
Tertiary reference. Used for what a symbol denotes in ordinary scientific practice and for which fields reuse it, never for a claim that any body assigns the letter its meaning.

Last reviewed 2026-07-31

Part of

Physical constants and quantity symbols

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Meanings

Common modern usageVerified fact

Denotes the magnitude of the electric charge carried by a single proton, and the negative of that carried by an electron.

Contexts: Mathematics, Laboratory

Officially standardisedVerified fact

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

Common modern usageVerified fact

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

Confidence

IdentityHigh confidence: High confidence because the identity is defined by a current official standard, but multiple independent sources agree.
Historical originModerate confidence: Moderate confidence because the historical origin is documented in encyclopedic references, but multiple independent sources agree, but early or supporting evidence is limited, but the regional or cultural match to this specific claim is not precise.
Current useHigh confidence: High confidence because the current use is defined by a current official standard, but multiple independent sources agree.
Visual matchHigh confidence: High confidence because the visual match is documented in encyclopedic references, but multiple independent sources agree.

Sources

ISO 80000, Quantities and units — recommended symbols
International Organization for Standardization · retrieved 2026-08-01
Paywalled and NOT READ. Registered so records can note that a recommended notation exists. It is widely departed from in practice, and no record types a meaning `official` on its basis. See docs/paywalled-standards.md.
The SI defining constants
Bureau International des Poids et Mesures · retrieved 2026-08-01
The seven constants whose exact values define the SI since 2019. Cited for the fact that a constant's value is fixed by definition rather than measured — a claim about the unit system, not about the notation.
Elementary charge
Wikipedia · retrieved 2026-08-01
Tertiary reference. Used for what a symbol denotes in ordinary scientific practice and for which fields reuse it, never for a claim that any body assigns the letter its meaning.
CODATA Internationally Recommended Values of the Fundamental Physical Constants
NIST / CODATA Task Group on Fundamental Constants · retrieved 2026-08-01
Authoritative for the recommended value and uncertainty of a physical constant, and for whether that value is exact by definition or measured. It fixes values; it does not decide which letter denotes which quantity, and no record cites it for a symbol's meaning.
Physical constant
Wikipedia · retrieved 2026-08-01
Tertiary reference. Used for what a symbol denotes in ordinary scientific practice and for which fields reuse it, never for a claim that any body assigns the letter its meaning.

Last reviewed 2026-07-31

Meanings

Visual description

Related & commonly confused symbols

Meanings

Visual description

Related & commonly confused symbols