Work, as a concept, is a rich and multi-dimensional idea. As a starting point, I will take the definition I once heard (from a priest, if I remember correctly), that work is simply the transformation of our environment.
Defined this way, work becomes an encompassing aspect of life. Work can be physical and tangible, as in the work of mining and refining minerals from the earth, or synthesizing substances in a chemical factory, or constructing structures from pieces of wood, metal and glass. Work can also be intangible, as in intellectual work, gathering and synthesizing knowledge in various fields of science, or sharing them with others in education.
Work has a similar definition in the physical sciences, where it means the transfer of energy when a force is applied to matter resulting in motion of a definite distance. The idea is similar, because it also involves a transformation; without movement or results, mere application of force does not become work. To perform work in physics is to transform the shape and location of objects in our surroundings.