Δ | "change in;" the value of a variable afterwards minus its value before |

Δx | a distance, or more precisely a change in x, which may be less than the distance traveled; its plus or minus sign indicates direction |

Δt | a duration of time |

Δ**r** | the vector whose components are Δx, Δy, and Δz |

λ | wavelength (Greek letter lambda) |

µ_{s} | the coefficient of static friction; the constant of proportionality between the maximum static frictional force and the normal force; depends on what types of surfaces are involved |

µ_{k} | the coefficient of kinetic friction; the constant of proportionality between the kinetic frictional force and the normal force; depends on what types of surfaces are involved |

ν | The Greek letter ν, nu, is used in many books for frequency. |

ν | a neutrino |

ν[bar] | an antineutrino |

ψ | the wavefunction of an electron |

ω | The Greek letter ω, omega, is often used as an abbreviation for 2π. |

Ω | units of ohms |

θ_{f} | the focal angle, defined as 1/f |

θ_{o} | the object angle, defined as 1/d_{o} |

θ_{i} | the image angle, defined as 1/d_{i} |

$ | the magnitude of the L vector, divided by h[bar] |

$_{z} | the z component of the L vector, divided by h[bar]; this is the standard notation in nuclear physics, but not in atomic physics |

a | acceleration |

a_{x}, a_{y}, a_{z} | the x, y, and z components of an object's acceleration; the rates of change of v_{x}, v_{y}, and v_{z} |

A | amplitude |

A | mass number (N+Z) |

A | units of amperes |

**A** | a vector with components A_{x}, A_{y}, and A_{z} |

§§A | handwritten notation for a vector |

|**A**| | the magnitude of vector **A** |

a_{r} | radial acceleration; the component of the acceleration vector along the in-out direction |

a_{t} | tangential acceleration; the component of the acceleration vector tangent to the circle |

**B** | the magnetic field |

cm | center of mass, as in x_{cm}, a_{cm}, etc. |

D | an electric dipole moment |

d_{i} | the distance of the image from the mirror |

d_{o} | the distance of the object from the mirror (technically from the plane tangent to the center of the mirror, although this seldom matters much for a mirror whose curve is shallow) |

d,p,m | other notations for the electric dipole moment |

D_{m} | magnetic dipole moment |

E | energy |

**E** | the electric field |

e | the quantum of charge |

e^{-} | an electron |

e^{+} | an antielectron; just like an electron, but with positive charge |

eV | a unit of energy, equal to e multiplied by 1 volt; 1.6x10^{ -19} joules |

f | the focal length |

f | frequency |

f_{res} | the natural (resonant) frequency of a vibrating system, i.e. the frequency at which it would vibrate if it was simply kicked and left alone |

F_{k} | a kinetic frictional force |

F_{N} | a normal force |

F_{s} | a static frictional force |

F_{W} | weight |

g | the acceleration of objects in free fall; the strength of the local gravitational field |

**g** | the gravitational field |

G | the constant of proportionality in Newton's law of gravity; the gravitational force of attraction between two 1-kg spheres at a center-to-center distance of 1 m |

h[bar] | Planck's constant divided by 2π: h/2π |

I | current |

J | joules, the SI unit of energy |

K or T | alternative symbols for kinetic energy, used in the scientific literature and in most advanced textbooks |

k | the slope of the graph of F versus x, where F is the total force acting on an object and x is the object's position; For a spring, this is known as the spring constant. |

k | the spring constant; the constant of proportionality between the force exerted on an object and the amount by which the object is lengthened or compressed |

KE | kinetic energy |

L | angular momentum |

L | the angular momentum vector of a particle, not including its spin |

m_{$} | a less obvious notation for $_{z}, standard in atomic physics |

m_{s} | a less obvious notation for s_{z}, standard in atomic physics |

M | the magnification of an image |

M_{a} | the angular magnification of an image |

n | a neutron |

n | the index of refraction |

n | the number of radial nodes in the wavefunction, including the one at r = ∞ |

N | number of neutrons in a nucleus |

p | a proton |

**p** | the momentum vector |

p | probability |

P | power |

PE | potential energy |

Q or ΔQ | the amount of heat transferred into or out of an object |

q | charge |

Q | the quality factor |

R | resistance |

**r** | the vector whose components are x, y, and z |

s | the magnitude of the spin angular momentum vector, divided by h[bar] |

s_{z} | the z component of the spin angular momentum vector, divided by h[bar]; this is the standard notation in nuclear physics, but not in atomic physics |

T | period |

T | the time required for a rigidly rotating body to complete one rotation |

t | a point in time, a clock reading |

t | torque |

t_{1/2} | half-life |

U or V | symbols used for potential energy in the scientific literature and in most advanced textbooks |

v | velocity |

v_{AB} | the velocity of object A relative to object B |

v_{x}, v_{y}, v_{z} | the x, y, and z components of an object's velocity; the rates of change of the object's x, y, and z coordinates |

V | voltage |

V | units of volts |

W | watts, the SI unit of power; equivalent to J/s |

W | work |

x | a point in space |

x, y, z | an object's positions along the x, y, and z axes |

Z | atomic number (number of protons in a nucleus) |

| is proportional to |

~ | on the order of, is on the order of |

m | meter, the metric distance unit |

kg | kilogram, the metric unit of mass |

s | second, the metric unit of time |

M- | the metric prefix mega-, 10^{6} |

k- | the metric prefix kilo-, 10^{3} |

m- | the metric prefix milli-, 10^{-3} |

μ- | the metric prefix micro-, 10^{-6} |

n- | the metric prefix nano-, 10^{-9} |

| (optional topic) unit vectors; the vectors with
magnitude 1 lying along the x, y, and z axes |

| a harder to remember notation for the unit
vectors |