Notation

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
Δr	the vector whose components are Δx, Δy, and Δz
λ	wavelength (Greek letter lambda)
µs	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
µk	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
θf	the focal angle, defined as 1/f
θo	the object angle, defined as 1/do
θi	the image angle, defined as 1/di
$	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
ax, ay, az	the x, y, and z components of an object's acceleration; the rates of change of vx, vy, and vz
A	amplitude
A	mass number (N+Z)
A	units of amperes
A	a vector with components Ax, Ay, and Az
§§A	handwritten notation for a vector
|A|	the magnitude of vector A
ar	radial acceleration; the component of the acceleration vector along the in-out direction
at	tangential acceleration; the component of the acceleration vector tangent to the circle
B	the magnetic field
cm	center of mass, as in xcm, acm, etc.
D	an electric dipole moment
di	the distance of the image from the mirror
do	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
Dm	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
fres	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
Fk	a kinetic frictional force
FN	a normal force
Fs	a static frictional force
FW	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
ms	a less obvious notation for sz, standard in atomic physics
M	the magnification of an image
Ma	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]
sz	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
t1/2	half-life
U or V	symbols used for potential energy in the scientific literature and in most advanced textbooks
v	velocity
vAB	the velocity of object A relative to object B
vx, vy, vz	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-, 106
k-	the metric prefix kilo-, 103
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