Stress is often represented by the Greek letter sigma (σ) and can be defined as the force applied over an area. When the force acts perpendicular to a plane, the stress is called a Normal Stress (σn), whereas when the force acts parallel to a plane, the stress is called a Horizontal Stress (σs). Generally, the stress acting on a plane is oblique which means it is neither parallel nor at a right angle to that plane. Therefore, the stress vector is resolved into normal and shear components that are aligned with the three cartesian axes: x, y and z. Since the shear stress component is generally not aligned with these axes, it needs to be resolved further into two components (see [[:File:GeoWikiWriteOff2021-Tayyib-Figure3.png|Figure 3]]). | Stress is often represented by the Greek letter sigma (σ) and can be defined as the force applied over an area. When the force acts perpendicular to a plane, the stress is called a Normal Stress (σn), whereas when the force acts parallel to a plane, the stress is called a Horizontal Stress (σs). Generally, the stress acting on a plane is oblique which means it is neither parallel nor at a right angle to that plane. Therefore, the stress vector is resolved into normal and shear components that are aligned with the three cartesian axes: x, y and z. Since the shear stress component is generally not aligned with these axes, it needs to be resolved further into two components (see [[:File:GeoWikiWriteOff2021-Tayyib-Figure3.png|Figure 3]]). |