phy. : force = mass * acceleration

Which means that the units of measurement for force (metric) are:

kilogram * meter
second * second

This means that the "weight" (pounds) used in America and England is a force (mass * the acceleration of gravity) whereas in Europe (and many other places) the mass (kilograms) alone is used to measure how heavy people are.

The mass unit in the English foot-pound-second system is called (ready for this) : the Slug. (not widely used, or even heard of; it's essentially being phased out) It's equal to 32.2 pounds or 14.6 kilograms.

The force unit in the metric system is : the Newton (widely used and fairly well known.)