6.1.1—Deformation is caused by tensile or compressive forces (forces and

A tensile force pulls along a body and tends to extend it; a compressive force pushes along it and tends to shorten or squash it.

Identify the force direction relative to the body axis, then decide whether the deformation is extension or compression. Real materials can experience both locally.

A hanging cable is under tension, while a column supporting a roof is under compression.

“Tension” is not a synonym for any force in a material; it specifically describes pulling stress along the relevant direction.