If a force is a vector quantity, thus having direction and magnitude, why do we express pounds/newtons, a unit of weight, as a scalar?

Question

It is in my understanding that forces are vector quantities, and thus have both magnitude and direction. Since weight is a force of gravity, it also must have magnitude and direction. Why do we define the weight of an object (through SI newtons or customary pounds) as a scalar, such as 5 newtons? Why, despite weight being a force/vector quantity, is the direction not specified?

Answer 1

It's just lazy language, the direction is implicit. If I say "the weight is 4 Newtons", then it's implied, because we're talking about weight, that the direction is "toward the center of the Earth". Similarly, if we say "the thrust on the airplane from the engines is 11,000 lbs", it's implied that the direction is "in the direction the airplane is going".

Answer 2

The units we measure a vector in are the units of its magnitude. For instance, magnetic field is measured in Teslas, which is also the unit for the magnitude of the magnetic field.

If we think of the unit as a multiplicative constant to a vector, this makes sense on a component-by-component basis:

\begin{align} \vec{v} & = \begin{pmatrix} 1 \\ 2 \\ 3 \end{pmatrix} \frac{\text{meters}}{\text{seconds}} = \begin{pmatrix} 1 \frac{\text{meter}}{\text{second}} \\ 2 \frac{\text{meters}}{\text{seconds}} \\ 3 \frac{\text{meters}}{\text{seconds}} \end{pmatrix} \end{align}