The load $\mathrm{P}$ produces normal stress in the axial member. Away from the pin, the normal stress acts on the entire area of the axial member. This area is termed the gross area. The normal stress away from the pin is computed from:

${\mathrm{\sigma }}_{\mathrm{gross}}=\frac{\mathrm{P}}{ {\mathrm{A}}_{\mathrm{gross}}}$

Note that the surface upon which the stress acts is perpendicular to the direction of the applied load $\mathrm{P}$; hence, the term normal stress.