On this Wikipedia the language links are at the pressure cooker food of the page across from the article title. This article is about pressure in the physical sciences.

A figure showing pressure exerted by particle collisions inside a closed container. The collisions that exert the pressure are highlighted in red. Various units are used to express pressure. Pressure is the amount of force applied perpendicular to the surface of an object per unit area. The symbol for it is “p” or P.

The IUPAC recommendation for pressure is a lower-case p. The minus sign comes from the convention that the force is considered towards the surface element, while the normal vector points outward. The equation has meaning in that, for any surface S in contact with the fluid, the total force exerted by the fluid on that surface is the surface integral over S of the right-hand side of the above equation. The pressure, as a scalar, has no direction. The force given by the previous relationship to the quantity has a direction, but the pressure does not. If we change the orientation of the surface element, the direction of the normal force changes accordingly, but the pressure remains the same.