But convection currents are ultimately at the mercy of temperature differences because these are what create pressure differences in the first place. The pressure difference between two locations is called a pressure gradient, and the force that actually moves air as wind is called the pressure gradient force.
oÂ·nus. n. 1. A difficult or disagreeable responsibility or necessity; a burden or obligation. 2. Responsibility for an error or fault; blame: Each side wants to avoid the onus of having started the disagreement. 3.
Medical Definition of callus. 1  1: a thickening of or a hard thickened area on skin. 2  2: a mass of exudate and connective tissue that forms around a break in a bone and is converted into bone in the healing of the break.