Originally Posted by DrDoppio
I usually tend to understand pound-mass when I say pound, much like majjo has pointed out. The reason for this is simple: when I buy a pound of apples at the market, I expect 453.59237 grams of apples, not 4.44822162 newtons of apples. How that is being measured is immaterial to me, as long as I'm not getting ripped off.
Ohhh, but you are actually getting that much in pounds, yes the force
of the Apples! The number derives strictly from the force the fully laden basket of Apples is applying to the scale. The force or weight weight of your apples is intrinsically the local force of Earth gravity and Apple gravity mutually attracting each other.
The mass of the Apples is their physical property independent of the effects of a local gravity well. Pounds or lbs is a force that intrinsically incorporates the gravitational attraction of the earth. Non-Earth vertical force scales can be calibrated to read properly in the vertical and then the force in pounds can be measured in directions other than Earth vertical.
So yes, pounds is a unit of force, a derived unit of force to take a quasi SI view of it, but nonetheless a unit of force.
And just the same pounds is a unit of mass, a sloppy nasty one, but yes a unit of mass as has been argued at length in previous posts.
Bottom line is the usage is very context dependent and that potential ball of confusion was a reason things like the SI system were developed in the first place.