| A {\displaystyle \mathbf {A} } | magnetic vector potential | tesla meter (T⋅m) |
| A {\displaystyle A} | area | square meter (m2) |
| amplitude | meter |
| atomic mass number | unitless |
| a {\displaystyle \mathbf {a} } | acceleration | meter per second squared (m/s2) |
| B {\displaystyle \mathbf {B} } | magnetic flux density also called the magnetic field density or magnetic induction | tesla (T), or equivalently, weber per square meter (Wb/m2) |
| C {\displaystyle C} | capacitance | farad (F) |
| heat capacity | joule per kelvin (J⋅K−1) |
| constant of integration | varied depending on context |
| c {\displaystyle c} | speed of light (in vacuum) | 299,792,458 meters per second (m/s) |
| speed of sound | meter per second (m/s) |
| specific heat capacity | joule per kilogram per kelvin (J⋅kg−1⋅K−1) |
| viscous damping coefficient | kilogram per second (kg/s) |
| D {\displaystyle \mathbf {D} } | electric displacement field also called the electric flux density | coulomb per square meter (C/m2) |
| D {\displaystyle D} | density | kilogram per cubic meter (kg/m3) |
| diameter | meter (m) |
| d {\displaystyle d} | distance | meter (m) |
| direction | unitless |
| impact parameter | meter (m) |
| differential (e.g. d x {\displaystyle dx}) | varied depending on context |
| d A {\displaystyle d\mathbf {A} } | differential vector element of surface area A, with infinitesimally small magnitude and direction normal to surface S | square meter (m2) |
| d V {\displaystyle dV} | differential element of volume V enclosed by surface S | cubic meter (m3) |
| E {\displaystyle \mathbf {E} } | electric field | newton per coulomb (N⋅C−1), or equivalently, volt per meter (V⋅m−1) |
| E {\displaystyle E} | energy | joule (J) |
| Young's modulus | pascal (Pa) or newton per square meter (N/m2) |
| e {\displaystyle e} | eccentricity | unitless |
| Euler's number (2.71828, base of the natural logarithm) | unitless |
| electron | unitless |
| elementary charge | coulomb (C) |
| F {\displaystyle \mathbf {F} } | force | newton (N) |
| F {\displaystyle F} | Faraday constant | coulombs per mole (C⋅mol−1) |
| f {\displaystyle f} | frequency | hertz (Hz) |
| function | unitless |
| friction | newton (N) |
| G {\displaystyle G} | electrical conductance | siemens (S) |
| universal gravitational constant | newton meter squared per kilogram squared (N⋅m2/kg2) |
| shear modulus | pascal (Pa) or newton per square meter (N/m2) |
| gluon field strength tensor | inverse length squared (1/m2) |
| g {\displaystyle \mathbf {g} } | acceleration due to gravity | meters per second squared (m/s2), or equivalently, newtons per kilogram (N/kg) |
| H {\displaystyle \mathbf {H} } | magnetic field strength | ampere per meter (A/m) |
| H {\displaystyle H} | Hamiltonian | joule (J) |
| enthalpy | joule (J) |
| thermal current | watt (W) |
| h {\displaystyle h} | height | meter (m) |
| Planck constant | joule second (J⋅s) |
| ℏ {\displaystyle \hbar } | reduced Planck constant | joule second (J⋅s) |
| I {\displaystyle I} | action | joule second (J⋅s) |
| intensity | watt per square meter (W/m2) |
| sound intensity | watt per square meter (W/m2) |
| electric current | ampere (A) |
| moment of inertia | kilogram meter squared (kg⋅m2) |
| i {\displaystyle i} | intensity | watt per square meter (W/m2) |
| imaginary unit | unitless |
| electric current | ampere (A) |
| ı ^ {\displaystyle \mathbf {\hat {\imath }} } | Cartesian x-axis basis unit vector | unitless |
| J {\displaystyle \mathbf {J} } | current density | ampere per square meter (A/m2) |
| impulse | kilogram meter per second (kg⋅m/s) |
| j {\displaystyle \mathbf {j} } | jerk | meter per second cubed (m/s3) |
| j {\displaystyle j} | imaginary unit (electrical) | unitless |
| ȷ ^ {\displaystyle \mathbf {\hat {\jmath }} } | Cartesian y-axis basis unit vector | unitless |
| K {\displaystyle K} | kinetic energy | joule (J) |
| k {\displaystyle \mathbf {k} } | wave vector | radian per meter (m−1) |
| k {\displaystyle k} | Boltzmann constant | joule per kelvin (J/K) |
| wavenumber | radian per meter (m−1) |
| stiffness | newton per meter (N⋅m−1) |
| k ^ {\displaystyle \mathbf {\hat {k}} } | Cartesian z-axis basis unit vector | unitless |
| L {\displaystyle \mathbf {L} } | angular momentum | newton meter second (N⋅m⋅s or kg⋅m2⋅s−1) |
| L {\displaystyle L} | inductance | henry (H) |
| luminosity | watt (W) |
| Lagrangian | joule (J) |
| L {\displaystyle {\mathcal {L}}} | Lagrangian density | joule per cubic meter (J/m3) |
| l {\displaystyle l} | length | meter (m) |
| ℓ | azimuthal quantum number | unitless |
| M {\displaystyle \mathbf {M} } | magnetization | ampere per meter (A/m) |
| M {\displaystyle M} | moment of force often simply called moment or torque | newton meter (N⋅m) |
| m {\displaystyle m} | mass | kilogram (kg) |
| N {\displaystyle \mathbf {N} } | normal vector | unit varies depending on context |
| N {\displaystyle N} | atomic number | unitless |
| n {\displaystyle n} | refractive index | unitless |
| principal quantum number | unitless |
| amount of substance | mole |
| P {\displaystyle P} | power | watt (W) |
| active power (real power) | watt (W) |
| probability | unitless |
| p {\displaystyle \mathbf {p} } | momentum | kilogram meter per second (kg⋅m/s) |
| p {\displaystyle p} | pressure | pascal (Pa) |
| Q {\displaystyle Q} | electric charge | coulomb (C) |
| heat | joule (J) |
| Reactive Power | volt-ampere reactive (var) |
| q {\displaystyle \mathbf {q} } | Generalized coordinates | varied depending on context (sometimes meter (m) or radian (rad)) |
| q {\displaystyle q} | electric charge | coulomb (C) |
| R {\displaystyle R} | electrical resistance | ohm (Ω) |
| Ricci tensor | reciprocal square meter (m−2) |
| radiancy | meter per second |
| gas constant | joule per mole per kelvin (J⋅mol−1⋅K−1) |
| r {\displaystyle \mathbf {r} } | radius vector (position) | meter (m) |
| r {\displaystyle r} | radius or distance | meter (m) |
| S {\displaystyle S} | surface area | square meter (m2) |
| entropy | joule per kelvin (J/K) |
| action | joule second (J⋅s) |
| apparent power (complex power) | Volt-Ampere (VA) |
| s {\displaystyle \mathbf {s} } | displacement | meter (m) |
| s {\displaystyle s} | arc length | meter (m) |
| distance | meter (m) |
| T {\displaystyle T} | period | second (s) |
| temperature | kelvin (K) or Celsius (C) |
| kinetic energy | joule (J) |
| t {\displaystyle t} | time | second (s) |
| U {\displaystyle \mathbf {U} } | four-velocity | meter per second (m/s) |
| U {\displaystyle U} | potential energy | joule (J) |
| internal energy | joule (J) |
| u | initial velocity | meter per second (m/s) |
| u {\displaystyle u} | relativistic mass | kilogram (kg) |
| energy density | joule per cubic meter (J/m3) |
| specific energy | joule per kilogram (J/kg) |
| V {\displaystyle V} | voltage also called electric potential difference | volt (V) |
| volume | cubic meter (m3) |
| shear force | newton (N) |
| v {\displaystyle \mathbf {v} } | velocity | meter per second (m/s) |
| W {\displaystyle W} | weight | newton (N) |
| mechanical work | joule (J) |
| w {\displaystyle w} | width | meter (m) |
| X {\displaystyle X} | electrical reactance | ohm (Ω) |
| x {\displaystyle \mathbf {x} } | position vector | meter (m) |
| displacement | meter (m) |
| x {\displaystyle x} | a generic unknown | varied depending on context |
| Y {\displaystyle Y} | admittance | siemens (S) |
| Z {\displaystyle Z} | compressibility factor | unitless |
| electrical impedance | ohm (Ω) |
| Z 0 {\displaystyle Z_{0}} | impedance of free space | ohm (Ω) |