Page "Continuum mechanics" Paragraph 18

Continuum mechanics deals with deformable bodies, as opposed to rigid bodies.

A solid is a deformable body that possesses shear strength, sc.

a solid can support shear forces ( forces parallel to the material surface on which they act ).

Fluids, on the other hand, do not sustain shear forces.

For the study of the mechanical behavior of solids and fluids these are assumed to be continuous bodies, which means that the matter fills the entire region of space it occupies, despite the fact that matter is made of atoms, has voids, and is discrete.

Therefore, when continuum mechanics refers to a point or particle in a continuous body it does not describe a point in the interatomic space or an atomic particle, rather an idealized part of the body occupying that point.