wrote in message ...

A body's mass is the measure of its inertia; which is the ratio of the
force
exerted on and/or by it to the acceleration that it causes;

You're referring to "inertial mass."

Mass is defined such that mv is conserved in particle collisions. Momentum
is then defined as p = mv. Force is defined as f = dp/dt.

Inertia is therefore a body's resistance to changes in momentum

See - http://www.geocities.com/physics_wor...rtial_mass.htm.

...which is equal to the body's weight, ..

Now you're referring to passive gravitational mass.

divided by the acceleration of free fall - due to gravity
- that the body is being restrained from. Mathematically: A body's mass
[m]
is a Constant; ...

Only in Newtonian mechanics. In relativity it's a bit more complicted. When
mass is defined as above then it is a function of the particle's speed.


Pmb