Why is W(Work done) is scalar?

W = Fs is not the definition of work done. It is just a simplified version.

The definition of work done is W = (integrate) F ds = F‧s (for constant force) = │F││s│cos@, where F and s are vectors (they are bolded),

In fact, this is the scalar product of two vectors, which yields a scalar.

Therefore, work done is a scalar.

Moreover, work done has the unit joules, which implies it is related to energy. Therefore, it should be a scalar.


P.S. the scalar product of two vectors is a scalar

The cross product of two vectors is a vector.