weight

{{Infobox physical quantity | name = Weight | width = | image = Mass versus weight in earth and mars.svg | imagesize = 300px | caption = A diagram explaining mass and weight | unit = newton (N) | otherunits = pound-force (lbf) | symbols = W | baseunits = kg⋅m⋅s−2 | dimension = \mathsf{MLT}^{-2} | extensive = Yes | intensive = No | conserved = No | transformsas = | derivations = }} In science and engineering, the weight of an object is a quantity associated with the gravitational force exerted on the object by other objects in its environment, although there is some variation and debate as to the exact definition.

Some standard textbooks define weight as a vector quantity, the gravitational force acting on the object. Others define weight as a scalar quantity, the magnitude of the gravitational force. Yet others define it as the magnitude of the reaction force exerted on a body by mechanisms that counteract the effects of gravity: the weight is the quantity that is measured by, for example, a spring scale. Thus, in a state of free fall, the weight would be zero. In this sense of weight, terrestrial objects can be weightless: so if one ignores air resistance, one could say the legendary apple falling from the tree, on its way to meet the ground near Isaac Newton, was weightless.