## Mass and Weight

Weight and mass are quite distinct concepts.
The mass
$m$
of a body is a measure of the 'amount of stuff' in a body.
The weight
$W$
of a body is a measure of the force, specifically the force of gravity acting on a body.
Despite being different concepts, mass and weight are related at each point in space by the equation
$W=mg$
where
$g$
is the acceleration due to gravity at that point and is equal to about
$9.8 m/s^2$
on the Earth's surface.
The above equation ignores all forces except the force of gravity. It would not be true for a charged particle in an electric field because the force would be at least partially electric, so would not be due solely to gravity.