So let us consider a member, and let's draw the internal forces acting at a particular section. We are showing the two segments; the left phase of the cut and the right phase of the cut. We're going to show the axial force, the shear force, and the bending moment. Now, this internal forces as we said already, they appear as opposite forces on the two phases. So in the case of axial forces, we have two possibilities. One possibility is that the axial force looks in such a way, another way would be acting in such a way. Okay. So that means the two forces are opposite to each other, right? Acting on the two opposite phase of the section. Now, we denote the axial force with the letter N, N stands for Normal. This force is normal, perpendicular, it means to the section. In order to distinguish among these two possibilities, we adopt a convention to call one of these two positive, we adopt positive to be this scenario. That means a scenario where the axial forces are pulling on both phases. They are pulling, they create tension on this phase, and pull on this phase create tension on this phase. So positive axial force, is the force that causes tension, while negative axial force is the force that causes compression. This convention is consistent with what we adopted when we talked about trusses thrust members where we called tensile forces as positive. Indication of shear forces force acting transverse to the axis of the member. Again, we have two possibilities. The shear force could appear either pointing downwards on the left face side and upwards on the right face or pointing upwards on the left face and downward on the right face. Again, in order to have a uniform language among engineers as to what type of scenarios we have. We adopt a sign, we adopt positive shear, to be the shear shown here. We denote the shear with the letter V for vertical or transverse if you want transverse to the member. We call positive the case shown here, where the shear force acting on the right face is upward, so left face downward, right face upwards. Negative shear, on the other hand, is on the right face downwards, left face upward. Finally, for the bending moment, again we have two possibilities either bending moments as shown here. That means where the tip of the arrow points to the top of the beam and the beginning of the arrow is at the bottom. This is, as we are going to see later, this is a bending moment that creates tension in the bottom and compression at the top. We denote the bending with M or the moments could be in the opposite direction. Again, of course, opposite to each other on the two faces. But in this case, the beginning of the arrow starts at the top and the tip at the bottom and this is what we call a negative moment. This creates tension as we're going to see later on the top and compression in the bottom. So we adopted a convention of what we call positive axial, shear and bending moment. Positive axial force, tension on both sides, positive shear force, upward on the right face, positive bending moment, a moment which creates tension at the bottom of the beam or where the tip of the arrow points to the top of the beam.