For axial members, the relationship between the internal force in the member and the member's deformaton can be expressed as:

$\mathrm{\delta }=\frac{\mathrm{FL}}{\mathrm{AE}}$

where $\mathrm{\delta }$ = deformation, $\mathrm{F}$ = internal force, $\mathrm{L}$ = length, $\mathrm{A}$ = area, and $\mathrm{E}$ = elastic modulus. This relationship is termed the force-deformation relationship.